There are frequent misunderstanding on why this should apply in match play--(stroke play is pretty obvious since there is a field to protect and everyone must play by the same rules to have a competition)
Obviously if you and I go to the first tee, and no one else is involved and agree to play a game by use of something other than the USGA(or R&A) rules, no one is going to arrest us-- We are just playing something other than golf under the Rules of Golf(just be sure you know what ALL the rules are before you start, otherwise you have no one to settle any disputes)--
However, if you are competing in a match, then the Committee(usually the club) has an interest in the Rules you play by-- It is in their interest to insure that their champion has been crowned in accordance with the Rules of Golf(not a champion of some other game which may or may not bear a resemblance to Golf--
If you waive Rule 1-3 then, in effect, you have agreed to change the Rules, and that is a waiver or change in the provisions meaning you are playing a different game.
Agreeing to overlook a breach, when both players are aware that a breach has, or is about to be incurred, results in the DQ of both players -- Dec. 1-3/4.
In match play the requirement to impose a breach and prevent any agreement to overlook a breach removes the onus of "being a bad guy" (Gee, I'd overlook that breach if it was me"). With the nonwaiver provision a player is required to enforce the Rules because the penalty to not do so is he is out of the competition (this is different than a breach in match play only, not known to the player, but known to the opponent, which the opponent can overlook and never raise--Dec 2-5/1)