I can completely understand the decision to use Parse. On the flip side of what the parent commented, big players who only have a comparatively limited presence in the mobile world don't always want to have to hire a full team just to implement their one or two simple apps. Conversely, a small player might not have the resources to hire a full team, or might not have the know-how or time to implement it themselves.

A team that is deeply invested in mobile might want to engineer their own solution. If you're a mobile-only company or even a mobile-first company, I would expect you to have a full backend team. Otherwise, contracting out the bit you don't have resources for just makes sense. That's where I see Parse sitting in the world, and with the client list you mentioned, it seems to fit perfectly. I wouldn't expect Home Depot to have a complete mobile team.