Take the case of an Active Directory server for a mid to large company. Say 10,000 users. If you have a query on process_events looking for something, and JOIN on users USING uid, the entire users table is going to be queried every time. Not cached, not filtered. Additionally, the V3.3.1 processes table uses WMI to pull data... try that on Win Server 2008 or 2012... kinda heavy if you are doing a bunch of process queries.