I have an identical twin, while we are 180 out on religion, politics and TV/internet viewing choices neither one of us are vegan or vegetarian.
My ex was vegetarian, no meat, chicken or fish. He just did not like the taste or how those protein sources made him feel. He was also proof you don't need those protein sources to get cut when weight lifting - WOW!
I tried, I really did, to go vegetarian. Two months in and I'm dreaming of hamburgers and I feel crappy! I caved and made a roast chicken meal for me and a vegetarian chili for him.
I felt great and he was happy. Since I was not a big fan of bacon it was no hardship to forgo bacon, he really hated the smell of it cooking.
I think everyone should try an elimination diet, just to see how certain foods make you feel. I use to love rice but I found I feel unwell in a way I can't describe other than unwell, so I don't eat it.
I love shellfish but again I feel unwell and an allergy test show I really should not eat shellfish, the reaction was high enough the doctor warned me it could cause an anaphylactic reaction.