I don't personally believe it should be absolutely required of anyone, aside from perhaps larger competitive events. I think individuals should pursue training if they are interested, and customers should decide whether that is a selling factor in the school.
One of the most effective things a school or training group can do to save a life in an emergency requires no special training, no scheduling, and virtually no money. Post a large sign stating to call 911 (or for those outside North America...whatever your emergency call number is), include the name of the establishment, the precise street address, and a directional pointer.
"In Case of Emergency: dial 911.
"This location is Sullivan's Karate, 123 Main Street, 2nd Floor, over the Mobil station in Springfield."
Adjust the address and directions as appropriate.
"This location is Delta Gym, 54321 Martin Luther King Blvd, between Broadway and Anderson Road, in Springfield"
"This location is the residence of Kim and Rob Jackson, 345 Sycamore Street at the corner of Walnut Street, in Springfield"