Pre Check TSA

Help me understand why I spent time and money filling out personal security information, had an interview in person and was fingerprinted, if, when I print my boarding pass, there is no special Pre Check designation?
I’m told it’s a random decision that I have to go through the standard airport security line, but despite the government determining that I am not a terrorist, 3 out of the last 4 flights, I was not given the Pre Check designation.
What is the point of bothering with Pre Check at all?
If, on the other hand, it was a consistent application, there would eventually be huge savings in time and personnel across the board.