They are made totally in mind with a person just walking by, seeing  an event occur, and just start opening it up. The Heartsavers essentially talk you through what to do, and after pad placement, just look to see what it suggests. Based on prompts from the unit it monitors, or suggests shocks. A class to teach 30 peeps how to use one usually took me 1/2 hour, and a lot of our saves were from folks who would never in their life think they would be defibrillating a dead peep back to life  In house they obviously need a victim, and a person to run the unit, but they have youths who have done this, to peeps over 90 documented, so they are really a first step approach to any cardiac sudden death, which almost always start in V  tach, V fib, scenario, which is what they serve.

In home I think they biggest drawback is probably price versus value/worth. As you said  a hefty price if never used, but how many times have you heard, Dad died at 47 of a heart attack, that metric can be served. Anyone having sport events. My Wife runs, and I cannot remember the times she came home, saying remember XYZ? He died at the finish line today. Huge market, mostly unclaimed, and price is probably the biggest factor. If I had any kind of store I would have one. In our litigious society, we are probably not far from liability if you don't have one, because they are available. Could have, should have, law.