It's much easier to solve physical problems when you make as many simplifying assumptions as possible. These reduce the complexity of the problem and the amount of error-prone bookkeeping, without, in context, materially affecting the outcome.

We all inevitably make a wide variety of assumptions of this type constantly when we work with any real-world system. They are a basic requirement for doing science and engineering. Literally every achievement of our technological society is built on top of a heap of simplified models of reality which are imperfect but usually good enough for the purpose demanded of them. We should celebrate them rather than moaning about them.

And then, in the appropriate context where it is meaningful, we can peel back our models and examine a richer situation.