Lighter bikes are more comfortable to ride - they feel nimble. Modern frames absorb bumps while still being stiff to allow maximum leg power to actually go thro

Lighter bikes are more comfortable to ride - they feel nimble. Modern frames absorb bumps while still being stiff to allow maximum leg power to actually go through the drivetrain instead of frame flex. Disc brakes make an enormous difference if you have long downhill sections or regularly ride in the wet. Sure there are diminishing returns, but better components really are better, and not just 20g lighter. High end derailers shift easier, chains have lower friction (especially in high/low gears), spokes and rims are more aerodynamic and stiffer, ratchets have smaller engagement angles, brakes require less force and don't overheat, tyres have lower rolling resistance and better grip, seat posts have compliance to remove chatter etc., And this is before you get into eg. MTB specific features like chain clutches and suspension tuning, or for triathlon aero bars, for city bikes pannier clips and built in lights, etc