Why is looking at porn considered cheating? Is this a universal feeling for women?

I'm 30, not married but gf lives with me and we have a kid. She recently found out I was looking at porn. Not because she found anything but because she pressed me on it when she came home later last night. 

We've lived with each other long enough for her to know when I am lying. My question is, do all women have an objection to their husband watching porn? I was doing it maybe 2 or 3 times a week. I looked at porn everyday before we lived together when I was single or not with her. I knew it was kind of bad doing it that much but this is obviously less frequent. Maybe I don't see all the effects because it hasn't happened to me but I would not care if she looked at porn if I was gone and the baby was taking a nap. She even told me she did before she moved in and we had a baby and it never phased me at all. 

I am curious because i always thought of the issue as depending on the circumstance, like well as long it doesn't interfere with the relationship. With my gf, I'm finding that it's just as bad as cheating to her.
user
Not sure if all women will feel the same
assistant
Why is looking at porn considered cheating? Is this a universal feeling for women?

I'm 30, not married but gf lives with me and we have a kid. She recently found out I was looking at porn. Not because she found anything but because she pressed me on it when she came home later last night. 

We've lived with each other long enough for her to know when I am lying. My question is, do all women have an objection to their husband watching porn? I was doing it maybe 2 or 3 times a week. I looked at porn everyday before we lived together when I was single or not with her. I knew it was kind of bad doing it that much but this is obviously less frequent. Maybe I don't see all the effects because it hasn't happened to me but I would not care if she looked at porn if I was gone and the baby was taking a nap. She even told me she did before she moved in and we had a baby and it never phased me at all. 

I am curious because i always thought of the issue as depending on the circumstance, like well as long it doesn't interfere with the relationship. With my gf, I'm finding that it's just as bad as cheating to her.
user
Is it considered cheating to my gf if my
assistant