I think a core reason (besides not knowing jj exists), is the framing that there is a choice that has to be made, or a switch that has to occur. It is, instead, additive. I have Sublime Merge (GUI git client) and jj both looking at my git repo all day. Zed's git stuff is watching it too.
jj is sort of a bag of git tricks for me that I use when needed. It's no different than some things being easier with the git CLI vs others being easier in Sublime. I'll be at a stage where my committing/branching/rearranging wants are something that jj nails perfectly, and I do those there. As far at the other tools are concerned, I just did a bunch of sophisticated git operations.
The "colocated with git" capability of jj is probably it's most amazing feature tbh, and is key to any sort of adoption.
jj is sort of a bag of git tricks for me that I use when needed. It's no different than some things being easier with the git CLI vs others being easier in Sublime. I'll be at a stage where my committing/branching/rearranging wants are something that jj nails perfectly, and I do those there. As far at the other tools are concerned, I just did a bunch of sophisticated git operations.
The "colocated with git" capability of jj is probably it's most amazing feature tbh, and is key to any sort of adoption.