I think most businesses are built "on the back of somebody else". That's the way commerce works. Think of things in the real world:

  - A store in a mall... depends on the mall operator to maintain and promote the mall
  - A auto parts manufacturer... depends on the auto manufacturer to sell parts and maintain the brand 
  - An MacOS developer... depends on Apple to sell Macs to supply a market.
  - A franchisee (e.g. McDonalds)... depends on the corporation to promote the brand.

The list goes on and on. Of course you have to assess the risk / rewards in any case before you decide it's worthwhile to move forward. But rejecting any business that depends on a platform (software or otherwise) eliminates many many business opportunities.