People eat what they eat for all manner of reasons.
I'm vegetarian. Originally for ethical reasons as a teenager, but nearly 40 years on, honestly, it's just habit. Meat is simply not something that I would think to eat - I no longer miss it and wouldn't want to start eating it again because I think it would be bad for my health and bad for the planet. Plus it's expensive and I don't know how to cook it.
If I were to argue that I'm still motivated by ethical reasons now, then I would have to go vegan. I really respect people who do, but I like cheese and yoghurt and eggs too much to sacrifice them entirely. I do try to eat more plant based meals where I can - I figure it doesn't have to be all or nothing.
DH is pescatarian. He eats vegetarian meals at home but sometimes has fish when out and about. He was raised veggie but then lived in a country where they put fish/fish stock in everything, and it was just easier for him to adapt. He has never had any desire to eat meat as well, so he doesn't. He doesn't claim that his pescatarianism is a moral stance, it's just about what he chooses to eat and what he chooses not to eat.
I have another pescatarian friend who eats fish on the basis that she would be willing to catch and kill a fish herself, whereas she doesn't think she could kill and butcher a cow or a sheep etc. I guess there is a logic to that.
I also know former vegetarians who have chosen to start eating fish because they think it's good for them. And meat eaters who have given up red meat because they think it's bad for them.
I think lots of us make fairly arbitrary choices about what we eat, really. Lots of meat eaters would choose to avoid eating horse or rabbit for example. And in the UK, nobody would eat dog or cat etc. Mainly because we feel a stronger sense of affinity with those particular animals, I suppose, but perhaps some pescatarians feel a sense of affinity with cows/sheep in a way that they don't feel an affinity with fish?!
As long as people aren't lecturing others on the superiority of their choices or preventing others from eating what they want to eat, I can't see that it matters, really?