Are you sure these are booking requests? Or are they Inquiries? You need to understand the difference. If they are booking requests, you have 24 hours to either accept or decline the request, and before that cut-off time, you can message with the guest. If they are Inquiries, you do not need to either pre-approve or decline- simply answering the guest's message within 24 hours is all you need to do if you don't want to pre-approve it.
Also, just because a guest sends a Inquiry rather than uses IB does not necessarily mean the guest hasn't provided ID or any other of your IB requirements. Sometimes guests have questions, and sometimes a guest wants to get a sense of the host before making a booking commitment. Some guests have encountered non-responsive hosts, listings that were not as advertised, scam listings, etc. and are cautious.
Just because IB is available doesn't mean all guests are comfortable using it.
@Jigisha0