If such arbitrary restrictions become a competitive disadvantage then they will go away.
On the other hand, for certain parts of the market, arbitrary restrictions have proven themselves a competitive advantage. Take the NES for example. Its lockout chip helped it get onto the shelves of retailers that were tired of low sales due to consumers' lack of confidence in the play balance quality of a randomly chosen Atari 2600 game.
Think how smartphones have largely absorbed the market for point-and-shoot cameras. No point in carrying two devices if one can do the job adequately.
Unless you don't want yet another $600 per year phone bill. A lot of people in Slashdot's home country carry a dumbphone plus a second device because most carriers are unwilling to offer low-minute voice-only plans on a smartphone.
Just because it makes sense for a mouse/keyboard setup doesn't mean it is the most logical way to multitask with touch.
But how is having a simple calculator application fill the screen, covering up the document you were working on, the most logical way?