Do casters do enough damage now to justify waiting around an entire day to get back a handful of spells? With few encounter-enders, I'm thinking it might be a hard sell.
Bingo. I think this is the reason why encounters per day is not really a front-page issue anymore. From what I've seen & read, a nova-ing caster can roughly keep up with the fighter on damage (much better vs. mook crowds, worse vs. 1 boss), and as mentioned control/debuffs are very limited/situational and usually won't affect bosses in any significant way.
So the GM doesn't have to worry about a fresh caster dominating a solitary big/boss encounter. Conversely, damage cantrips mean the caster can fight all day long (granted it will suck so hopefully the GM isn't going overboard).