Lots of good suggestions for general travel. good bag, packing cubes can be hugely important, depending on the trip.
But to answer OP's original question -- yes, you're being a sissypants. As far as I can tell, you're thinking about getting a bag because you had to spend 3 minutes washing things occasionally?
If you're traveling through multiple climates, or camping, or need to bring a laptop for some reason, I'd totally get a good bag and some cubes to stay organized. But for backpacking in SE Asia?!? I've backpacked in SEA for six months with a 30L bag, and that was with a quite a bit of camera gear.
Here's what I brought to Indonesia for 2 weeks this year -- 1 pair swimsuit (that looked more like shorts), 1 pair board shorts, 2 t-shirts, 1 long sleeve button-down. smart phone and charger. wallet and passport. I did bring a small backpack, but seriously considered just stuffing everything in my pockets.