You could breed "primates" in all sorts of numbers if you wanted. Especially the smaller species. Some fit in your hand. That's really not the issue. The issue

You could breed "primates" in all sorts of numbers if you wanted. Especially the smaller species. Some fit in your hand. That's really not the issue. The issue is that they have very complex social and behavioral demands, and yes, more so than pigs or dogs. It is easy to make a colony of dogs in a laboratory live a very happy life. I've seen it, and I can't see a big difference between a companion dog and a lab dog much of the time. They are just as friendly and outgoing and play all the time. With monkeys that's a lot more difficult... Which is why research in primates is a lot more restricted and more heavily regulated. You need (more) specialized facilities. You also can't handle them as easily because they will bite, poop or hit (the bigger ones) you.