Magic armor does, yes, but that looks like pushing the goal posts. 5e was built around ignoring the possibility of magic items at all, at least per WotC at the time. It's never assumed and until AL rules allowed specific magic purchases and XGtE covered that as well it was a DM only determination. It's still a DM only determination becaue XGtE isn't guaranteed to be used and AL games are not everyone's games, but those guidelines don't show a proliferation of magic even going with them.
We need to assume the DM allows for or places the armor before the player buys some. IME, it's usually the player who pays for it.
Your planar binding exploit you were applying to bards in your bard thread would equally apply to wizards if a DM allows for massive funds that way, completely nullifying the point you are trying to make even if wizards spent all these funds on scribing, which it generally in addition to the standard.
Wizards are not struggling as a class and spell versatility isn't going to change that. "I think it steps on wizards' toes too much" is probably the best argument against it but that's a perception opinion. Mechanically I'm not seeing the issue, even if a PC changes out the entire list during extended downtime.
You realize that nobody is arguing against it by saying that the same logic wotc was using to make spell versatility per long rest to account for campaigns that level slowly should be applied to cantrip versatility and cantrip versatility should also be on long rest rather than on level to account for the fact that wizards can also play in those slow leveling campaigns.