system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: There are many gregarious mammals, birds and fish. Why so few gregarious reptiles?
gpt
Reptiles rarely live in social groups because they rarely raise their young. Instead, most reptiles lay lots of eggs and then abandon them to the wild. The young survive because of the sheer number of eggs that were laid. But they don't grow up socializing with their parents or siblings, and remain solitary the rest of their lives. 

It's just a different method of survival which has worked for most lizards. It's not necessarily better or worse than forming social groups. There are also some lizards who are raised by parents and form social groups, but they are the exception, not the rule.