The only one even in the game I can think of ATM is 
, which is probably a huge contributing factor to its prevalence. It is basically the only option available to a support wanting an affordable utility item that wont put them over the CDR cap.
Mig892 votesThe thing is almost every support can utilize CDR over any other stat. Even tanks and damage dealers because you cant afford the really expensive damage items and CDR is usually a cheap stat.
TotalJerk1 votesProblem is when I'm approaching 40% CDR or outright just don't need any more I'm still basically forced to spend gold on it.
Just getting 
/
/
and 
alone put you at half the CDR cap.
There are 6 item slots, 40% CDR is the cap, and there is only one support item in the entire game that doesn't give CDR. That means that it is basically going to be bought every game.
Mig891 votesTheres a rune that converts it into damage and imo those boots are garbage for almost any support because of how available CDR is. Its better in almost any situation to grab any other pair of boots. I dont think its really ever smart to "rush" CDR
BeatzBoyFTW2 votesCDR's literally a juicy stats for supports who're in dire need of having their high cooldown spells to be up at all times, what're you on about.
TotalJerk1 votesWhen I already have 40% CDR I don't need more of it, obviously. It's actually pretty damn hard to not overcap when playing support as I blatantly stated in the OP.
BeatzBoyFTW1 votesI don't see too much harm if it's just 10% additional CDR, I rarely have any problems of "gathering up about 60% or more CDR in total". Other than that, the additional CDR benefits Transcendance Rune a lot in terms of granting bonus AP & AD.
TotalJerk1 votesYou don't see any harm in forcing supports to waste gold on useless stats?
BeatzBoyFTW1 votesTo me, it's just a damn minority. You don't see Relic Shield being a problem to abusive solo laners despite not utilizing the execution passive.
TotalJerk1 votesThere's two supports in every goddamn game; that isn't a minority. I just want them to add more support friendly items that DON'T have CDR.
OniZetsu6661 votesI think the reason for that is the keystone Transcendence.
TotalJerk1 votesNaw. This has been a problem since before the new runes. Actually when there were support items that gave 15-20% CDR this was an even WORSE problem.