Client refusing their email.

I have been in business for myself for around 3 months. Things have been going well, had a few male clients act a little weird but nothing I cant handle and I end up firing them. Anyways I came across a new situation. I ask the client for their name, phone number, and email as always. With the email they hesitated and sat quietly for a minute then went "...can we skip that part?" I let the client know that the email is for the booking info and receipts but ok. After I got off the phone my immediate thought was "why would they decline revealing their email?" I could ask them but at the same time I dont want too, maybe he has been hacked? Or maybe I am over thinking. Has anyone else come across this situation before and what was the outcome?