Why does my boyfriend feel the need to lie about watching porn?

I’ve asked him out of curiosity quite a few times since we’ve started dating. His response was always “Like twice, never really got into it.” Then he finally tells me that he’s been watching it throughout our entire relationship(almost 9 months). I’ve tried asking him what’s up, but all I got was “I don’t know” or “It’s just a bad habit.”

He said if it bothers me he won’t do it anymore, but he’s said this about a few things before and failed quite a few times before following through, or coming clean.

We’re intimate with each other and have sex any chance we get, except he rarely ever initiates it. I even try and try and spice things up by pleasuring him out of practically nowhere. I’m head over heels for the kid but I have no idea what the issue is. Any help?