Personally, when I play Udyr I go madstone. It allows you to secure a VERY early solo dragon, farm your jungle faster while being full (meaning you can counterjungle, gank, and countergank with full hp + mana everytime), and lets you not worry about your mana/hp in jungle. While people who go madstone and don't gank or get dragons can work, that requires full on constant farming and your lanes to go even at least.
So while madstone has problems, it makes up for those assuming a mildly competent jungler.
my point is I see so many people mad stone, but they don't do anything you just said. they don't control dragon, they don't counter jungle, they don't split lanes, nothing. they just farm their own jungle and when they do peek out they get kited for days and they become an easy kill. it's literally the worst of both worlds for a jungler. no gank potential and no map control whatsoever. on top of that, they are squishy.