Apparently you work at Justin.TV. I don't know how big your individual projects are, but personally, I didn't get unit-testing religion until I started working on really big stuff, close to the limits of what I'm capable of. I worked for a year on a 60,000 line program, and it started getting painful. I worked for another year on a 100,000 line program, and that's when I finally had to relent and start writing unit tests.

Here's a common scenario that made me want to write tests. I want to implement feature A, but to make it work, I'm first going to have to write library B and C. So I write library B, but there is no way to test it in the program yet, because feature A doesn't exist. Right after I've finished the code, I have a pretty good idea of where things might go wrong, and what corner cases I want to exercise. But by the time I finish library C and then get around to implementing feature A, I've forgotten that stuff. Pain points go unaddressed.

In summary, unit tests really start to show their value when you're working on a program that's too big to fit into your head all at once.