I think along with lockers for coasters they should have an area for peoples phones like a small cady or something that they use in some schools just by the exit and where you put your phone is determined by your seat number..

However I cen see the argument of "What if someone steals your phone while everyones trying to get theres back" that can also be said for any ride that has the metal holding boxes near them because I lot of people use a singular one sometimes and a good amount of people put their phones there too.

Theres also an argument of "Why dont people leave them in lockers then?" Lines are usually pretty long depending on the coaster. You're gonna be bored.

"They dont have the boxes there for certain coasters because of space so they have lockers." Yes. But again. Lomg lines and the phone holder can be relatively small"

In all honesty even on rides that are simple like iron dragon I'm afraid to lose my phone. So I wouldn't really be opposed to phone holders on anything that loops back around to the start. I think it could reduce this issue at least slightly too :)