Or,
a. you're not a regular customer and he didn't want to be bothered to do it.
b. he profiled you as a customer, decided you were probably not buying today so he gave an excuse.
c. honestly doesn't know how to do it, which I seriously doubt.
It is quite possible that a random employee of a shop, watching the counter, until a driller or some other knowledgeable employee returns, does not know what a PAP is or how to measure it (2 very different things: he may know what it is but not know how to measure it.)
I can tell you if you randomly walked into my shop and weren't a regular or someone I was "working with", I would charge you to do it or tell you I would do it when you bought a ball.
Understandable and reasonable.
Just doing it for you would rank right up there with measuring someone's hand and giving them the measurements so they can order and have a ball drilled from the internet.
You might ask why he wanted to know and you might tell him that: unless you were using it to drill a ball for him to get the proper reaction, you will not measure it. As a bowler, I would not ask that question unless I wanted to know it, during the course of buying a ball from you and having it done correctly.
On the other hand -
If I wanted to know that and asked you , a knowledgeable driller to do that, I would expect to take 30 - 60 minutes of your time to do it right and expect to pay an hour's worth of service - $50 - 75.
But that's me. I know what a driller is and what he works at to learn and to do right. I know it is often a thankless job with the vast majority of people thinking, in ignorance, there is nothing to it. It is part of the disrespect to which most people in this industry in the United States are subject.