> I liken this to a hotel that decides to make their own lightbulbs.

The key differentiator between AirBnB and a hotel is the community. By adopting a more flippant variation of the well-known humanist sans-serif fonts, they're communicating that their experience is more about the people and the connections than just the physical infrastructure of a boring old Helvetica hotel.

Having their own typeface is good strategically because it helps to create a moat around the product experience.

It's similar to how Wal-Mart created their own typeface to double down on their American-as-apple-pie branding. Now every time you drive past a Wal-Mart, the font tells that story before you even walk into the store.