Comment 3 for bug 1358890

One reason for keeping them separate is that it'd be easier to miss what the alarms/reminders relate to if they've been folded up.

Another is that you might want to snooze one of them, but not the other. I'd be fine with snoozing all or none, but with calendar reminders you might have per-event snoozing rules, which at some point we should probably respect.