[kps]

/opt showed up as a place for packaged software, where each package (directory) has its own bin/, lib/, man/, and so on, to keep it self-contained rather than installing its files in the main hierarchy. ~/opt is just a per-user equivalent, analogous to /usr/local vs ~/.local.

The advantage of /opt is that multi-file software stays together. The disadvantage is that PATHs get long.