This is about keeping these “players” playing in order to get an open convention where they will try to slay TRUMP.
You brought up an excellent point and reminder.
Romney “fixed” it in ‘12 in order to stop insurgent Ron Paul by show time, (at convention).
Yes, it’s all about RNC GOPe control.
Sad thing is, the lessor candidates will hang in there helping the RNC GOPe to screw with the outcome hoping their guy and screw the leader.
In the end, their guy will get screwed too.
Then we wind up with Rubio or Bush.
After March 15 the primaries will be winner takes all. Open convention is a fantasy. The calendar favors Trump.
It explains why the GOPe have had their candidates fight against each other so hard instead of attacking Trump.
Every one who gets 10% takes a delegate from Trump.