I posted about inquiring guests who don’t reply yesterday so I’m glad you brought this up.
I decline if the guest doesn’t answer. It’s frustrating because my calendar is tied up for a day or until I decline. I don’t think you need to call like you do to cancel an IB.
I recall reading in the past that frequent declines hurt our search rankings, but I don’t see that currently on the “help” page regarding search rankings. It doesn’t hurt your response rate so long as you accept or decline.
I think a lot of guests don’t realize they requested to book rather than instant booked. Unfortunately, we can’t get their phone number until they book to try and reach them and tell them to check the app.