Quantum theory

I know this is a bit of a physics question and it’s not the topic of the site, but because you understand the subject, I’m asking you.

1. Why assume that before a measurement the electron is in a superposition of eigenstates and after the measurement it collapses to a particular eigenstate with a certain probability, instead of simply assuming that it was always in an eigenstate, it’s just that we didn’t know that until the measurement.
2. According to the uncertainty principle, it is impossible to measure the position and momentum in space (any 2 operators are not commutative, but we will take them as an example), but why assume that there is uncertainty in nature? That is, we can assume that we have uncertainty in knowing the position or momentum, but this is simply because we cannot measure it. But there really is a certain position and momentum. That is, the uncertainty principle only exists with us and not really in nature. Why not understand it that way?