In some disciplines, carrying a bottle is just part of the setup. In others - running a marathon, grinding through a trail race, the run leg of a triathlon - it isn't. The gel exists for those moments. Compact, no mixing, nothing to manage between aid stations or checkpoints. 45g carbohydrates in a 2:1:1.5 ratio, 343mg sodium. Same intake as the drink, same place in the protocol. You just don't need a bottle to get there.