Or- and hear me out with this one- they prefer an explanation which follows naturally from existing experiments and doesn't require a hacked together non-linear irreversible operation which occurs only under bizarre conditions exactly when needed to patch over experimental results. No one in the whole world cares if the universe is deterministic or not, but collapse is embedded in an entirely deterministic system. MWI may not be right, but collapse is wrong.
It’s quite nice to have something irreversible though. It gives you time. Also nobody really thinks QM is the end of it, assuming semi classical physics under the hood is just odd to me. There is something below QM that we don’t understand yet (AdS/CFT looks like a good start to me) and personally I think the whole interpretation of QM debate will look stupid in retrospect. Yeah collapse is odd, but it just shows us this isn’t it. Reality is much weirder than we thought and giving up on realism is just the beginning.
You get time from all sorts of technically reversible things though! Even in a totally classical universe entropy gives us an arrow of time. Under MWI decoherence is reversible, but is functionally irreversible in the same way entropy is.
You're right though, I very much doubt QFT as it stands is the bottom. However, that doesn't mean the current debate is stupid. Whatever underlies QM, you'd still expect the measurement effect to also be an emergent property. The debate about whether atoms existed is still meaningful even though we now know that "atom" isn't a perfectly natural category. Indeed there are protons and such underling the physics, but the protons do pretend to be atoms much of the time, and thus pretend to do all the things we use atoms to predict.
Similarly, MWI and collapse (as well as, if less so, weirder theories) can be good explanations as to why a quantum phenomenon occurs even if there's also a reason they happen.
OK other than the several holy wars and church schisms and most of the physicists of the early 1900s including Einstein. And quantum-woo obsessed people on the internet. The point is that all the quantum stuff still adds up to mostly deterministic classical physics. Maybe only quantum physicists get to have free will, so long as they make decisions based on the exact results of their experiments?
Actually, if you eliminate collapse entirely as a non-linear operation, then you have a new huge problem for QM: there is plenty of non-linearity in the universe (e.g. double pendulum experiments, not to mention GR), and QM predicts that there shouldn't be any non-linearity at all, if you eliminate wave function collapse/the Born postulate.
Ahh, linear in the differential equations sense, not the affine function sense. Trigonometric functions are quite linear- they decompose into a basis! That's why, for instance, Fourier transforms are useful for more than signal processing.
