Why would it be awesome if everyone got free ice cream in their favorite flavor whenever they were sad, but terrible if everyone got a pill to take that made them happier whenever they were sad?
Because ice cream is soooo tasty
Seriously, though, I think it has a lot to do with not taking the easy solution, but working to solve your real issues. A pill that is guaranteed to make you happy is not solving the underlying problem if one is truly depressed or unhappy about something. It just ends up forming a dependency (as does ice cream for some people). Even anti-depressants are not meant to be a long term solution, but a stop gap measure when someone is really stuck in a downward spiral. Most respectable psychiatrists will not simply prescribe an anti-depressant and then send you off. They will work to figure out what is making you depressed and then help you solve that. Also, the great thing about brain chemistry, which is different from most other autonomous body functions, is that (as Scattercat pointed out) it can be changed by your behaviour. So, isn't it worthwhile to learn how to do this yourself instead of being enslaved to big pharma? I guess, for me, it comes down to this: If I am stuck on a deserted island, do I want to be doomed to a life of depression when my pills run out?