They used to--Race for the Taste in October, Tower of Terror 13k in October--but they got rid of them (and replaced it with Wine & Dine 1/2). Since Disney has decided that running is a draw, they are doing what they can to maximize the profit. 10k doesn't have the same draw as a "destination/vacation" race as a half marathon. It's not just the race--it's how many people they can entice to make it a vacation (and spend all that money!)
Maura