Persian Instrument Vs Foreign Instruments

[Mezrab]

I was checked this part of forum but i didn't find anything about Persian instruments, I thing it's good that we talk about these kind of instruments in English, there are some topics that we can start by them, one of them that it is so important is why we don't want to mix or make songs by using both of the foreign instruments and Persian instruments? are there any problem with them? what's the reason and what cause it?