The point is that I don't need to be able to visit or physically mail anything. But it is just one more point of trust and something I can more easily verify.

Frankly, I'd be okay with a P.O. box if it is clear it is a small business operated mostly from someone's home.

It simply, at least here, is something that allows you to verify things like a company actually being registered at that address.

Another thing is that geographic location matters. For things like data protection laws and other laws the company I want to do business with might or might not follow depending on the country they are based in.