The field I work/play at has a general rule of semi only. In recen years with the number of modes out there, they have loosened that rule for private parties, and they can use whatever firing mode they would like as a private group.
I have had guns for years that I could easily switch to ramping or full auto, but I have never found the need. In a lot of cases, we have players show up with barrowed equipment and they have no idea how to control firing modes. I have been on the receiving end of so many excessive strings of paint from Ions and E-Tippmanns it's rediculous. Generally full auto and ramping lead to total lack of fire control in new players I have noticed.
I had a guy put a dozen rounds into my ribs last year from about 20' away with an Angel he had no idea how to use. Prior to that playing an event that did allow full auto - I got to receive about 15 rounds to my right shoulder from a E-Tippmann from about 12' away.
Sometimes It's Good to be EVIL