Fully agree he should withdraw if he’s mathematically eliminated. After all, both Kasich and Cruz have said that’s the right thing (heck, in Cruz’s case, that’s the moral thing) to do.
The fact they don’t practice what they preach is incredibly telling. They are both hoping to be anointed by the GOPe rather than being the choice of the people.
Cruz knows he has no chance of being anointed by the GOPe, which is why he is fighting them tooth and nail at these state Conventions. Cruz understands that if he doesn't fight for the seating of his delegates, the GOPe will put their own delegates in those spots.
Trump on the other hand is convinced that he will win on the first ballot, so he has done nothing to protect his interests on any subsequent ballot. Should no one get the magic 1273, then you are going to see Trump's delegates abandon him for Kasich - not Cruz's delegates.