When ever I get a champion like Varus, Nidalee, Sona, Lux, Galio, etc etc, I'll go ahead and take clarity so I can spam my abilities for longer than I normally would be able to. Not to mention refilling my ally -insert mana hungry champion here- 's mana as well. It really helps keep the pressure on.
Why does it seem like no one else use it? o:
Beatrix5 votesJust get a 
as your first item. It's not like 
is a terrible item to eventually build into. With the map's natural mana regen buff, you can pretty much spam forever. Then you're free to take summoner spells like flash and barrier, both of which can totally save you if you get caught out or pulled in.
Direwolfiez1 votesChalice on Sona or Soraka = almost infinite sustain and a crap ton of assists. I usually get at least 7-10 assists before I die, so it's really a great idea.
Balderdash10004 votesIt's because there's plenty of mana items out there. Get a tear, chalice, or catalyst to start and your mana issues are pretty much taken care of for all but the most mana hungry champions. Add the occasional relic, or complete your mana item, and your mana issues are gone. There's no need to waste a summoner spell on something that is so easily taken care of.
Direwolfiez4 votesI always take Flash and either Ignite, Heal or Barrier. I've never used any other Summoner Spells on ARAM, ever. I know that Heal causes a debuff, but even if you need to Heal someone while it's on, the utility it provides is more useful, in my opinion, than what Clarity gives. I've only run into mana issues with mana hungry champs early game; after that I never really have them again, so it's only useful for about 1/3 of the game. If 3/5 of my team has Heal and I'm the ADC or long-range APC, I take Barrier to make sure I can stay alive long enough to put out decent DPS, and I take Ignite if I'm a burst mage with low to medium range.
2WhiteAndNerdy2 votesA few possibilities.
Just a few from the top of my head. The first two probably aren't the case. At least... I really hope they aren't. I normally take Clarity if I'm playing one of my caster champs, which is almost all of them. Mainly because in ARAM casters are the main damage dealers until the melee champs start to get some items and levels. Spam 'til you drop!
Jakethenight1 votes6.They don't realize Heal is nerfed on Howling Abyss due to the debuff. Every ARAM has someone who doesn't realize this. :\
Marthian2 votesI take it for my allies.
Phatdiamond1 votesI take clarity on certain champs that spam a lot. Tear doesn't provide enough mana regen to keep up with Sona or Velkoz.
SpecterVonBaren1 votesOnly time I take Clarity is when I get Swain in ARAM, and even then, as someone else said, I only really use it at the beginning for the most part. The reason I take it is so if I'm in a situation where I need to keep my ult on for just a little longer or something similar then I have it.
BigDaddySenpaiii1 votesI take it with almost every mana based champion. It gives you a good advantage early game because you can basically spam your spells. (even with chalice, most mana users will go low on mana very quickly).
On champions that aren't as mana intensive, like AP Nasus, Fiddlesticks, TF, it allows me to start 3 Dorans or wand/tome, to give me me a AP and build advantage.
By endgame it's not as useful but there's plenty of times, even as ADC (Varus, Jinx, Sivir) where I lack the mana to continue a push or kill streak and it really hits the spot.
BTW non stop Varus/Sona harass > your petty heal/barrier. And while you are building mana regen I am building brutalizer (V) or lichbane (Sona) and dominating.
Aspynn1 votesI've seen more clarity users playing adc than something like a mage. Pretty much any mage I play in aram I go for tear and rely on the health packs for big boosts of mana until I'm high enough level for tear to be enough. I always start tear on mages like ori lux and syndra in aram.
BigDaddySenpaiii1 votesTo be honest I don't understand why tear is even purchased outside of champions that actually scale off mana (Ryze, Singed, Blitz) or ones that actually are huge mana pool dependant (Swain, Anivia, Karthus) or use an on hit build with Manamune (Ez, Urgot)
Chalice will give you MR and a much better mana regen (huge mana pools mean nothing when you are OOM). Also, AA staff is kind've weak. The AP conversion isn't very good, no CDR (compared to 20% on grail) and the shield isn't going to do anything for you when an assassin jumps on you. Most of the time I just see enemy mages dying with 90% of thier 10k mana pool.
Aspynn1 votesThose are good points and I understand what you mean. Maybe it's just my noobyness but I have always preferred Tear on most mages (at least on aram) I used to build it on like literally everyone <.< (adcs and tanks too) I just usually feel like when I have tear, I never go oom. And when I have chalice, I actually have to manage my mana. I understand skill spamming isn't always a good thing to do, but in ARAM its always nice to poke whenever you can. I still do take chalice on some champs, I just usually prefer to take tear on champs like syndra ori and lux. If I play someone like soraka or sona I usually go chalice.
NinjaToad991 votesIt can work if you have super mana hungry champions that can't necessarily get mana regen (like if they're AD and have no use of manamune or essence reaver). However, most mana hungry champions can just get a tear or chalice and be able to spam all day long. And those that can't always have the relics (Although that isn't super reliable as somebody could be low on HP and need it more then you do).
ceaselessphantom1 votesIt has been such a long time since I played aram. I probably would not take into consideration the reduced healing and take it.
With how strong healers are on the map regardless of it it is hard to take into consideration the reduced healing.