This is one of 5e's biggest flaws & why concentration as implemented is so silly. Everything is tuned so far towards enabling facerolling everything as the gold standard that anyone with a character trying to be a force multiplier rather than some guy solo'ing near a bunch of mooks is doomed to failure because there's no point in caring enough to bother with those schemes. For whatever reasaon WotC keeps pushing the idea that 5e casters are still 3.x style optimized well played extreme end LFQW god wizards & CoDzillas. That misguided uest causes silliness like the feat that started this thread & well meaning GM's trying to "fix" the problem wotc is obviously concerned about at their tables.1) Concentration checks aren't usually difficult, it is just that when you have to make a lot of them the threat of failing goes up.
2) I DM a lot of games for a lot of different people and it is very rare for players to actively defend the casters. Most people IME do not actively use good team based tactics in 5E because the consequences of failure are so mild. Most combatsexist to eat up a few resources rather than test the party.