I’ve yet to see one close to pitch side on most of the cattle pastures I ref on (low level local adult teams in the US) but the college and High School games tend to be in college/school stadiums that may have an AED - but maybe not that close to hand if we’re on the outer fields… which brings me to what I really want to say which is learn CPR!
As we’ll as reffing I’m also a volunteer for the local Fire Dept and we have refreshers each year on amongst other things, CPR/AED. We immediately start CPR after a collapse and if available we use the AEDs as well, but the paramedics stress that AEDs often don’t restart the heart so be prepared to just keep plugging away until the ambulance turns up with.
So - AEDs are great to have available but, please, learn CPR.