Even within the production company it changed. Jeopardy has Johnny Gilbert do introductions, Wheel has Pat Sajak talk to the players.
Seems like production company. Goodson-Todman almost never had the announcers do it. Exceptions: Double Dare, I suspect because Johnny Olson had so little else to do, and TPIR, obviously a unique case.
What shows besides $otC had the models introduce the contestants?
I want to say Elaine Stewart introduced the couples on Gambit.