Why is the reverse phone number lookup a paid service?

I guess the short answer to that question is that “it’s a paid service because someone has figured out a way to offer the service and charge for it.”

If you just enter the phone number itself in a Google search window, you might be pleasantly surprised to see how much can be found out in that free manner. At least, you should be able to find out something that way if it’s a land line. Probably no luck if it’s a cell phone.

@CWOTUS right, it’s a cell phone, I tried that. How frustrating.

800notes is a site where people report unwanted calls usually coming from 800 (including 888, 877, 866, etc) numbers, but also many using other prefixes. Many of those calls are scams. You can find out here if your prank caller is one of them.

Sometimes people have dug further and managed to find out who the caller is. That will be reported on this site.

www.whitepages.com has a free reverse phone # search.

Because it would take you a bit to do the search in that book for a specific number. It is not sorted that way, sothe paid service provider has done that for you. As noted, there are plenty of reverse search sites available.
You can always just dial the number and say:
” I am creating my own phone book and you are in it!!!, who are you?”