Bit of a counterpoint - I haven't read most of the bestiary entries, but typically in previous editions, the first or primary attack is typically the worst - be it because they have a higher attack, higher damage, or a rider effect (grab/trip/save/etc. if hit) than subsequent attacks, or are required to land before using even worse attacks (say, a giant kraken first needing to grab you before swallowing you whole).
One of the things in general for x/day things is you never want to end up doing that thing you do in RPGs - saving items for "emergencies" then end up with 99 of them and only needing 2.
Personally, I look at it this way - If I have a thing I can do X times per day, that will only do one thing, recovering it long rest, while at the same time having 2 lvl 3 spell slots that's much more flexible with how I use them, also recovering them at the long rest. I'd worry about not using the latter effectively enough than the latter.
Not saying "You're doing it wrong!" or your thinking is critically flawed - my time with characters casting spells in 5e has been rather limited compared to other editions.