Over on Whatever (you are reading Whatever, aren't you?) John Scalzi makes the best argument for going the regular publishing route I've seen yet. The joy of foreign sales.
Not all agents do foreign sales. And yes, they'll take a portion off the top. Okay, so your agent gets you a contract to sell your book to Botswanna, and you get $2000. The agent takes 15%, or $300, maybe a little more. So you go home with $1700. No agent, and you're probably not getting that sale. So, is it worth it? Hmm, $300 to get $1700, or nothing. Yeah, I'll take the $1700, thank you.
This is like some people who have said they don't want to play the lottery, or take a chance on winning a house, because if they win they don't want to pay the taxes. Hello? What? And the political argument about making more than $250,000 and paying more taxes. Really, you're going to take a paper hat job because you want to keep your tax liability less than 20%. You know, I've gone between tax brackets before. And just hitting above the current one sucks. It really does. But really, $250,000 a year and you think that's middle class? Um, nah. That isn't the richest, but that's pretty damn rich right there.
Sorry, got off track there.
But yeah, it's the agent's job to find markets for your work. They only get paid when they get you money. And then it's a percentage, they have a vested interest in your career and your income now and in the future. Really, better than sliced bread.
There are times when you should go a different route, many very legitimate. However, if you can go the other way, you should try it.