I suspect they rely on Apple for this - it has to be licensed and everything and Apple has little incentive to be perfect here. They'd rather you have a HomePod and an AppleTV I think. 🙂
I know Roku doesn't publish specs on their players, but I have 4(!) of them.
The cheap kitchen TV is very new. I have a very old TCL Roku TV (maybe 5 years) and that one has had this issue forever. I have an express in the bedroom, but haven't used it for Airplay yet. The TCL TV has a 4K stick (brand new) - I bought this one because Youtube and some other apps were getting slow on the built-in Roku. Sadly, it has this problem as well.
My best guess is that out of all of these, the ONN TV's Roku has the largest amount of onboard RAM. The only other difference is that the kitchen TV is almost primarily used for AirPlaying podcasts (I didn't plan it that way... just found that podcasts + kitchen work is just not TV content friends). But that also might point to a memory issue - I never run other apps there so perhaps that leaves plenty of free RAM for the Airplay app.
Sadly I can say the TCL TV has been doing that for a few years, so I'm not sure there's a fix coming. The 4K stick is new, but has been doing this since I've had it (4 months?).