The whole point of doing it this way - via the tax companies' own services - is to make it an advertisement for those companies, so that once somebody starts earning more, they would preferentially pick them. It's also a form of mild lock-in, since already having their return history etc there makes filing that much easier, creating an incentive to pay.

In the meantime, the same lobbyists who created this scheme are trying to prohibit IRS from developing its own free filing system:

https://news.ycombinator.com/item?id=19613725