When I tell people I work on Bitcoin full-time, a somewhat common reaction is "Really? I thought Bitcoin was finished, what do you work on?"
I spend half my development time working on new stuff (or testing new stuff that other people have submitted), but the other half I spend trying to anticipate problems or reacting to problems that are reported. That work tends to be unseen, partly because we want to keep problems quiet while we fix them and partly because quietly anticipating/fixing problems minimizes the 'lulz' that attackers might enjoy if every single-node-DoS attack caused us to run around like chickens with our heads cut off.
Anyway, good developers are hard to find, and one of the reasons I'm not thrilled by all of the AlternaCoins is because I'd rather a good developer help make Bitcoin better rather than spend their time with the busy-work of cross-porting the latest Bitcoin fixes to some other codebase. I would guess that some of the developers of the alternative chains underestimated the amount of work it takes to nurture them and keep them healthy. Maybe that will change when Bitcoin is truly mature and has dealt with another year or two or six of attacks and scaling issues...
I truly don't mean this to sound like a threat, but I think some of the blockchains that have been chugging along running on an ancient forked version of the Bitcoin codebase will be attacked; pretty soon we'll be fully disclosing the denial-of-service bugs that prompted the 0.6.2/0.6.3 releases, and it is highly likely somebody will decide to play with exploit code on a vulnerable chain.
I wish people would find more constructive things to do with their time, but I wish I could fly and never get old like Peter Pan, too.