Yes, you do need an Apple device to use Maps, but it's at least a viable alternative to Google that casual users pick (versus, say, OpenStreetMaps).
How much is the cost to continually verify every business on Maps? I would expect it to be a very large amount. If it were very expensive, would Apple have created Maps, or keep Maps operating? I don't know.
I guess what I'm getting at is that Apple doesn't get much direct gain (as far as I know -- maybe they get some money from Yelp?) from Maps, and I'm rooting for Apple because at least they're not Google.