Minimum bike weights serve 2 important roles other than "it's just the rules": 1) Fairness: While differences between bike manufacturers are large, the competi

Minimum bike weights serve 2 important roles other than "it's just the rules": 1) Fairness: While differences between bike manufacturers are large, the competition is about primarily athletics & setting standards allows less well resourced rider teams to compete. 2) Safety: Lighter bikes may compromise on strength/safety. Tours are already dangerous enough as is, a bike breaking poses a danger to all riders on the course not just the rider. Weight minimums ensure that there's not an attempt to drop the structural weight below safe limits. That said, weights can be decreased over time if there are legitimately new weight saving technologies that do not compromise strength of the bike.