Following UX Best Practices?

I was activating my EPF account today. The primary mandatory field doesn't allow pasting. I had to type in the whole number digit-by-digit from another screen, which had more chances of error.

I could find no reason as to why would you disable pasting. The only reason I can think of is to avoid some special invisible characters that may get copied or to make sure there are no trailing spaces. This can be handled easily in validation (even GPT-3 can write the code).

This pattern is common on other websites too, is there any specific use case handled by this limitation? I can imagine why Stackoverflow would ban copy-paste, but what's up with simple forms?