There's almost no one on when I get on (late evening west coast), and I play for short enough windows that I don't want to sit and wait for strikes and games to finish up.
I actually enjoy it a great deal solo, but this raises the other reason I prefer to play Destiny solo, so far. When I have a poor experience, the majority of the time it's because other players are in the mix, particularly higher level players. When I was say level 20 and got paired with level 25+ guys, it utterly ruined the experience. I felt like their little kid brother running around trying to help out as they mopped the floor with everyone. Not fun. Likewise, doing patrols or public events and having those guys rumble through and just annihilate everything. When I play I make a point to avoid overlapping with lower level players so as to not poach on their encounters (aside from public events where we all chip in).
Other than the time slots I have to play, I've actually had a bias for playing solo, because I've been leveling much more slowly than you guys. Once the level spread in characters gets over 2, it's really hard for it to be enjoyable. I alternate between feeling like a fifth wheel, totally inconsequential to the battles or I am cowering behind a rock, under-equipped for what I'm up against. The latter is better now that my gear is up to snuff (I finish about half the strikes without dying), but the leveling system really drives a wedge between players. Once I'm caught up to level 28 or so, I'll make more of an effort to get into the mix with you guys.