Experienced users (developer or otherwise) of unixy systems already know what lsof is. Inexperienced developers only need to learn it once, then they join the ranks of the aforementioned. Using these sort of systems for any length of time in the capacity of a developer or even just a hobby enthusiast will effectively make you a 'sysadmin', at least w.r.t. knowing the basic standard tools. Not least because lsof is useful for many sort of tasks (like figuring out which program is using a drive you're trying to umount), so chances are high that people in these situations already know about lsof.

And besides having to learn that lsof exists, you'd also have to learn that this even more obscure tool exists. And what happens if you prefer for the program to terminate itself gracefully, cleaning up whatever mess it might have made, instead of sending SIGKILL? Now you have to look up the PID or program name anyway, probably using lsof..