I've actually often wondered why it wasn't. My parents have had to miss voting many times (both local and national) due to work actually since they both practically have two 40 hr/week jobs, working for their regular companies and then leaving there to go do work at the fire department (dad's cheif, mom's in charge of money). I think they had to miss the last local election even though it was very important to both of them to try and get a certain person out of office. They talked about it often before the election day, trying to figure out when they each might be able to go, and complaining that they'd probably miss it due to all the work they had been given. And yep, they had to miss it.
istarted a thread really similar to this about a week ago, but it got no posts... anywho, DONT ROCK THE VOTE