It has much less to do with interest than it does access. You can go to the park (or a rec center) and play one on one with a friend and a $20 basketball that will last for 5 years whereas you need a much larger group, more equipment that costs a lot more money, a field that needs a lot more maintenance, and decent weather to get in good baseball practice. Not to mention the fact that you almost have to be on a travel team to get exposed to decent competition in baseball and if you go to the park or the Y, there's a decent chance you'll run into a dude who is bigger, better, faster, and stronger than you to provide a better level of competition. It's just a completely different financial realm as JBears already pointed out.