Originally Posted by
alij2018
Isn't ot more tough to climb?
No. 50x34 yields a low gear like 42x29 which is sufficient for most mountains including those in the Colorado Rockies and European Alps.
Big cassettes let the pro peloton eschew small ring use, avoiding the potential for a stage losing chain drop as with Andy Schleck in the 2010 Tour de France 15th stage.