When I started my OW cert and got to the part about "never dive alone" I was like - "WTH?". I’ve always been a very self-reliant person. From growing up as a commercial lobsterman on the Maine coast to solo winter camping in the Montana wilderness. Diving is no different. Training, equipment, and mental attitude go a long way.
That said, I am MUCH more conservative when alone. Know my limits and stay WELL within them. Had a solo dive just the other day: Wanted to test some new equipment and experiment with different weights. Deepest I went was 20 ft but spent most of the dive between 10 and 15 ft. Easy CESA if I had any problems.
I talk to a lot of folks who say "But diving is a social activity." - bullcrap. Not for me. Socializing is fine for parties or get-togethers at your local dive shop but when I dive I like to be on my own. I will still look for buddies to dive with but if I can’t find one I’ll still go.