The ability to match based more on ELO than other criteria favors protecting high ELO players from the higher risk of being randomly matched with low ELO players....and losing. This benefit has to come with a price.
Any person who puts ELO as the primary criteria should have to maintain the highest total wait times across a period of time than most other players. That means being ready to partake in a game against other players with similar ELOs for more hours per month than other groups of players with significantly lower ELOs. Hopefully this would also translate to playing more games, and that would of course risk their high ELO against other very good players.
Now you have a balance where ELO is being protected AND also still being risked.