Originally Posted by carpediemracing

It's useful if there's no feed zone and you need a bottle, typically in a crit. If you "steal" a bottle from a spectator who happened to put one down on a curb or on the road then that's not a feed. I've only resorted to this once but managed to grab a "road" bottle in a flat, fast, Cat 123 crit (before the days of pros racing with the amateurs). I've also passed up a bottle "accidentally" left on a hay bale (mid turn in a left-right chicane - it wasn't a racer that put it there).

It's also good for picking up dropped stuff on group rides, like if someone drops their saddle bag or minipump or bottle or phone or whatever.

It's hard picking up a bottle if your butt is still on the saddle. It's much easier if you drop down to the top tube - that's the key to doing it smoothly regardless of flexibility.