I can't comment on the band stuff but as far as waxing and waning interest that is a big thing right now for me. I'm a bedroom player. I don't think I have the skill to play in a band. I'm older and started later so I don't have the ability or flexibility to play hours on end to get significantly better. Originally when I first started playing all I wanted to do was play a few campfire songs, that was going to be enough. But then it wasn't and I wanted more because it as fun. After a number of hiccups I eventually found my way to the electric and this website (which is why I have 3 electrics and 2 amps
) and was a having a lot of fun. But lately that changed a bit, and it was becoming more of a routine than fun. I went away on vacation for 2 weeks and thought I'd be back enjoying playing but it just seemed like I was playing the same old thing. I thought this article was right on for me
Why I quit playing guitar
Everyone is going to be a bit different in why they play but I think for most of us it comes down to loving to make and hear music whether it's a simple chord progression that has special meaning to you or being able to play Petrucci note for note. If you lose the love you won't enjoy playing. Right now I'm off on a mission to rekindle that since I do love playing and I have to accept my limitations and find things that don't make it feel too much like work. I know I find that again and so I'll keep playing. Ultimately I've never played for anyone but me and so long as I'm ok with what I'm doing and I still (slowly) learning I'll keep at it
In terms of "don't have the skill to play out" depending on what you want to do that might not factor in. There are plenty of not amazing guitar players i see in bands (myself included) and if you want to imprive, you'll improve much faster when you're in that scenario.