Also, you underestimate the effect of laziness. A company really has to do some atrocious thing to result in people leaving its services. Like, what would make the average person change from Gmail? He/she may not even know that 1) it is part of google which should be avoided now 2) what are alternative email providers 3) the whole change requires quite the technical know how.
It is simply naive to expect that “the market will solve it” to work in the general case. Competition only works when there are strict rules. Otherwise, the strongest/least fair player wins, and that’s why monopolies have to be broken up.