Season runs from Mid March to early May and is about 11 or 12 weeks. Back out spring break (although many teams play games that week) and you are talking 3 games a week. 1 week of rain and suddenly you can find yourself playing 5 or 6 games in 8 to 10 days.
Several things jump to mind immediately: Pitching - how many places have enough for that? Practice - when does that happen? School - games typically involve a 4 or 5 hour commitment sometimes more with travel whereas practice is usually 90 minutes or so. When do kids do their work? Cost - adding 10 games will probably cost school districts such as the SED $15,000 dollars or so. Each school will spend $750 on umpires (5 home games X $150) and $500 on travel ( 5 away games X $100 for the bus). Coaches might want more money too.
None of it is insurmountable - but there are people that will argue against for these reasons and they won't be crazy.