I don't understand why that is as a male?

If I go for a massage I expect it to be all over. I lived in Thailand for many years and had various styles of massage but was always free to ask or deny.

Back here in the UK I've never even thought about it, always assumed it was necessary. If an area was missed I have asked and pointed to it.

Of course, the more sexual massage is often offered for extra cash. That has happened in even the more reputable places.