In a word, yes. My preference would be to either dive with a competent buddy or be in a teaching/mentor role with a less experienced diver (with the dive agenda targeted beforehand). I do enjoy sharing the underwater experience, but I do not want to be put in the position of babysitting someone through a dive - therefore, I do dive solo on occasion.
I agree with the poster that said as an instructor, you are essentially diving solo. Agree with that premise, having instructed for 20-some years. The flip side of that is having been an instructor, I do feel a tinge of guilt diving solo as a primary tenant while rising through both YMCA and NAUI training was "never dive alone." I get over it, but the guilt tinge is there.
I also agree with the poster that was an UW photographer. When I am shooting, I am a lousy buddy. Worse when my buddy is also shooting. That is "same day, same ocean" diving - which is another term for solo diving. We may enter and exit together, but we were not functioning as a buddy team.
Over the past couple of years, I've found myself in a position to solo dive much more frequently. I've ended up on charter boats in North Carolina and more recently in Panama City where I don't know any of the other divers on the boat. I'm at the point in my life where I don't tolerate incompetence well - and I see quite a lot of that these days on charters. Rather than take on an unknown - and potentially incompenent diver - I prefer diving on my own.
Unlike other posters, I do not set arbitrary limits on solo activities. Conditions dictate how I dive and how I manage my time underwater. I find the notion that diving at 34' vs. diving at 30' is inherently more dangerous to be somewhat silly. What is that depth where it finally becomes too dangerous??? To me, there are other conditions - visibility, currents, task-loading, etc. that have more of an impact than setting some silly limit.
Bottom line - I enjoy diving with others and given the choice to dive with someone competent or dive solo, I'd choose the buddy (more likely for social reasons than safety).