...because Trumps message is limited.
“ Polititians are stupid ! Build a wall, send illegals home and then bring them back again”
That’s his message at EVERY rally every time...nothing else.
.. just that.
It’s called staying on message; a stump speech, and is a basic tenet of political campaigns. Cruz does the same thing with cliches such as “Washington Cartel”, Jeb with “proven record”, etc. they all do it. If you follow a candidate closely, you will hear the same comments over and over.