I really don't see why. If you like the game enough that you very much want to finish it, you probably should be paying†. For those who are money-poor but time-rich, they do offer a free option. But if you have more money than time, they want you to cough a little of the abundant resource up in exchange for the scarce one. (If you have neither money nor time, I would posit that's your real problem, not the pricing structure of Tiny Tower.)
† I don't mean this in a moral sense, but in a "it's a reasonable expectation and quite possibly essential to the business plan" kind of way
I think the complaint was about games where as you progress, the time cost increases until even the most time-rich player isn't prepared to keep paying it. Advertising these as 'free' is kind of disingenuous, even if it's technically correct.
† I don't mean this in a moral sense, but in a "it's a reasonable expectation and quite possibly essential to the business plan" kind of way