Probably because there is no demand. My local municipal government was recently looking for someone to maintain their website, which is little more than a simple blog. The job description essentially laid out the job as your basic, run of the mill CRUD application. The kind of stuff kids in high school do for fun.

When you read down to the requirements section though, they were asking for a CS degree and a bunch of other stuff you would normally expect to find from a $200K/year job at Google, not a mediocre pay, small government job. The fact that they can actually ask for such ridiculous requirements and fill the position speaks to there being far more supply than demand, at least from my point of view.