Currently, almost all support items have CdR, and ALL CdR-possessing support items have 10% CdR. This is good, as CdR is support's core stat - their contribution is not based around scaling numbers (be it with AP or AD), but around using their abilities for their non-scaling effects. As such, they want (and benefit) from having as much uptime on them as possible - which is where CdR comes in. And with 10% CdR on virtually each of their items, they are able to choose their items for their other benefits, without having to worry about CdR.
A similar thing goes for tanks, btw.
Beyond supports, there is another upside of having plenty of CdR in the game: It makes balancing easier. With a lot of CdR in a variety of items, the balance team can reasonably expect that a given champion will have at least 20% CdR in the mid-to-late-game. This enables them to tune ability cooldowns so the abilities are not used overbearing early (when champions don't have much CdR), but also not too long for the later-stage fights.
A good example for this is Shen: Before CdR became abundant, Shen's ult cooldown was shorter (180-120 seconds, back in S2, down to 162-108 with 10% CdR (which was what conventional Shen builds could get back then)). Nowadays, his cooldown is longer, but he has more access to CdR (200-160, but down to 140-112 with 30% CdR). Now, Shen doesn't start with 30% CdR - in fact, he starts with 10% at most, making his early ults more infrequent than they used to be, and lessening his early impact on other lane. However, with him purchasing 2-3 CdR items, his ult's cooldown will scale back to its previous, late-stage appropriate value.
Also, on your items:
Warmog's is hardly bought right now, even with the CdR. Swap the CdR for HP, and you'll see it being bought even less - most champions are not interested in a pure HP stat stick, even with Warmog's passive.
Frozen Heart had always had high CdR, and should keep it. It is barely build right now, anyways.
Knight's Vow, Zeke's, Glory, Banner are support items, see above.
Abyssal and Adaptive have CdR, so that the presence of CdR is not a decision point for deciding between the two and Spirit Visage. Remove CdR from them, and you'll see that their purchase rates pummel, especially for early purchases. Remember, tanks are also based around the utilty impact of their abilities, like supports. They are a class that should have easier access to CdR.
Banshee's could lose its CdR, true. Same for Protobelt.
Zhonya's cannot lose its CdR, as it serves as a padding stat to prevent the item being to efficient in either offense (if replaced by AP, see old Zhonya's) or defense (if replaced with Armor).
Maw is in the same boat as Zhonya's.
Duskblade got specifically changed to have CdR. Why? To have it become a more viable first item for ability-based assassins, instead of auto-attack based carries. And Youmuu's always had CdR.