Originally Posted by
Koyote
Right. And so why not just run 2x and get closer spacing with a better chainline? I've been running that on my gravel rig from the start, have ridden over plenty of rough stuff, and have never dropped a chain.
Clutched RD's provide better chain retention and reduce chain slap.
Narrow/wide front rings provide better chain retention than shiftable front rings.
1x systems also allow for larger rear tire clearances, and have less things for mud to get gummed up in.
Shifting a 1x drivetrain is more simple, which is beneficial when navigating difficult terrain.
Of course some people prefer 2x for the tighter spacing and don't experience any of these problems (or don't feel a need to solve any of them, or find the trade off unacceptable). Shimano still makes front derailleurs for their MTB groupsets too and I know some XC MTB racers prefer to run 2x for the reasons you state. There doesn't have to be a one-size-fits-all solution here.