This is a meme that isn't 100% true. There are many many companies out there that have, yes depended on a 3rd party API, but also built something incredibly valuable, profitable, and even reaped financially from it (see Buffer, Hootsuite, Radian6, AppAnnie, etc)

No, it probably isn't going to last forever (then again, what company is?), but the alternative is... not building a business and waiting forever until they discover an idea that has no 3rd party dependencies AND has lots of demand (ie probably never).