Well another factor could be that Perforce is a lot easier to use than Git - Actually, would like to think am good with git, but sometimes just wonder how it became so big considering the simple or important things (like check-ins and merges) are so complicated.
check-in isn’t a concept in git because there is no server in git. It’s just a log. The beauty of the merkle tree. It’s just GitHub became popular because people didn’t understand that you can rebase from any remote source.
Delta patches become effortless