oh I see. lawns have to REQUIRE the use for them?
I use a stick edger each and every week on all my lawns. not because the lawns require it. but because I personally feel an edger does a much straighter and much sharper job than any man of any skill level with a trimmer could ever do.
I see plenty of guys in my neck of the woods who use trimmers instead of edgers. personally in my neck of the woods you could easily get by with edging only once or twice a month. there is very little growth to edge week to week but a stick edger will do a better job in my opinion.
I don't think require is the right word. I've seen guys use walkbehind edgers every week, others choose stick edgers and still others trimmers. it's a matter of what you feel does the best and quickest job.