When I was in my 30s and 40s, I could have sex 3 or 4 times a day, while my girlfriend and later wife liked it only once and maybe twice on the weekends. She also used to get frequent migraines and then not feel like having sex. Occasionally, we would have an argument and then she wouldn't feel like sex. There were times when we were both stressed from our jobs and didn't have the energy for sex. For these reasons, I would masturbate at least once every day. I never ignored her when she was ready and willing, which was most of the time. Masturbation takes a lot less energy and time than having sex and guys will use it for sexual and stress relief. It feels good and relieves stress. Now that I am in my 60s, I don't want to waste it with masturbation and I've only done it about 4 times in the past year, as her headaches are long gone, we are retired and we make up after an argument very quickly.
If a guy is masturbating and ignoring the sexual needs of his partner then there is a problem, either with his state of mind or with the relationship and it needs to be resolved. If he does it and does not ignore his partner's needs then it is not a problem.