How come they don't wait for a tag up and advance more often? Man, there could be many correct answers to this question. What if you're tagging up, but the outfielder drops the ball? You end up at second base if you're lucky, hopefully you don't get thrown out on the force play. Tagging up from first is very hard to do. You need a deep, deep, fly ball and an outfielder with a poor arm to advance.