My main factor is I don't want to have to context switch across applications. I don't feel like I'm doing that if I stay in the terminal. As such, I would imagine if I were a VSCode user, I'd prefer a git plugin there.
VCS is very much tied to the code, so I think it makes sense to co-locate.
There is a small learning curve for the commands but it's minor compared to the intuitive control you get. A lot of the dedicated tools are just too bloated and use different terminology than the git standard which baffles me.
My colleague will use source tree and Everytime I see him doing stuff I always think : "But that's not what the got command is called for that".
I use helix as an editor and like to use a range of command line tools and scripts for regular stuff. Lazygit fits right into that and I don't have to leave the terminal.
I used vs-code a few years ago and its got plugin was (I assume still is) pretty good, if I used it as my editor then I'd probably use a plug in like you say, but as things are lazygit is both an awesome tool and the path of least resistance.
I'm glad people still build these TUIs, that's exactly what i need, simple interaction with my keyboard, no fuss, no bloat (edit: just checked, the executable is pretty large ~5mb, I wish Go made some effort in that area), a simple executable that can run on my headless server through SSH