lol not true. By 12 minutes into the game, players should be around lvl 9 so they will their ults leveled.
Anyways, regarding your question:
All current standard supports have strong utility abilities (whether its a heal, shield, CC, or some ability that protects their allies). Coincidentally, these champions all deal magic dmg and have some type of ap scaling in their kit. I think by champion design, most standard supports are designed to be high utility magic dmg dealers. If we dig a little deeper into the AP vs. AD champion comparison, you might notice that majority of magic dmg dealers have higher utility and base ability dmg in their kits. In contrast, AD champions should have slightly lower base dmg on their abilities but are compensated by the fact that their autoattacks deal more dmg due to their item builds. This is probably the main reason why we don't see AD supports.
DISCLAIMER: What I'm about to mention regard AD "support" champions is pure theory crafting.
There is an extremely small pool of AD champions (maybe 1-3 at most) that would be "okay" as supports but it takes alot of skill to properly execute.
these are AD champions i'd consider potential supports: Lee sin, GP, Gnar,