Having unused imports adversely affects code readability, as their presence is confusing. Code that is never used should be removed to keep codebases clean and maintainable. Unused imports may also negatively affect compilation time and impact the ability of the compiler to perform accurate incremental compilation.
Note that there are cases where importing "unused" units is necessary:
Register procedure
need to be imported at least once for code in those locations to be executed.
Remove the unused import.