The number of snapshots/day is limited by their start time, so the slot limits do control the number you can run.

You can have unscheduled snapshots, so you can define more than you can run.

Since packages can't install a schedule (users have to schedule them once installed), not having all schedules running in DE orgs shouldn't be a problem.

Enterprises can get more slots.

On a more conceptual note, the slots are designed to:

1) space out load over the hour when they are scheduled

2) make orgs space out work across the time available

3) make sure orgs don't affect other orgs when scheduling

When we looked at the reasons customers would want to schedule at one time rather than another, we kept coming back to the problem that many orgs would want dashboards, reports, and snapshots all run at between 6 and 8 am on Monday morning, for all their users. To avoid overloading the service, we wanted to make sure that the load is spread out, and that companies can look at their own processes and decide when to schedule items, given the constraints.

DE has one slot mostly we thought that DE orgs will test something, then want to stop it. If you want to test your package - a whole system of triggers, snapshots, scheduled apex, reports and dashboards, then you'd install in an EE org to make sure it all can run.