In farming, sharecropping is the low risk way to grow your business. It is the landlord that takes on much of the burden if the crop fails. But with small risk comes small reward.
In technology, "sharecropping" is the high risk venture. The landlord here assumes no risk at all if your application fails. The burden falls squarely on you. However, with the high risk, if you hit it big, the payoff potential is huge.
So while there are some parallels, from a business point of view, working with someone else's platform is nothing at all like sharecropping.