SpotHero spent A LONG time very quietly struggling to line up initial supply, deals and product. Years. During that time they seem to have figured out that commercial spots, and making the commercial parking experience 10x better was the opportunity. Then they went after it.
@swamp40 - I agree, and it's great to see that spot hero has taken off in Chicago. Likewise, ParkWhiz has been doing very well. I'd attribute their success to migrating their focus away from the "I'll list my spot online so you can rent it" model to the commercial parking lot and garage yield management space.
Both startups allow users to take advantage of the former model, but they've been able to meet demand by working with parking lots and garages.