The argument espoused is that is would make the regular season "better". Just because the result of the game may have some implication for either team, it doesn't mean the game itself (level of play, coaching or officiating) will be better.
Maybe its different down here, but I have never seen an SIAC or PAC school not giving 100%. Two examples...
(1) Two weeks ago, we beat Vincennes Lincoln and there was a missed call that cost VL a TD. Bobref admitted the ref was out of position. HUDL confirms the ref made the wrong call. What if that game cost VL a spot in the playoffs?
(2) Like Cathedral and Dwenger, we are by far the smallest school in our class due to SF. Depth is a huge issue and probably cost us last year in Semi-State against MV Fortville. We have more than the normal amount of players who are banged up and could probably have used a week off last week, but we played 5A Castle in SIAC "Rivalry Week". None of those kids sat out, because for us a game against Castle (in any sport) means a lot.
Coaches, players, officials, fans, etc. really can't give 110%. The argument that the regular season would be "better" assumes they can.