I've almost never been comfortable with picks my whole life.
Even when I was gigging alot the only time I'd use them is when my fingers broke down.
Now I've been using a thumbpick off and on and have decided for me, if I ever use a pick, that's what works best for me.
I never put in the time to learn to be a good standard hybriid picker.
It was like why? I already spent all those years learning to finger pick, and to me its a superior method because as noted above, it gives you an extra finger, actually two fingers that normally would be pinching a flat pick.
The thumb pick doesn't interfere with my style at all and makes those fast chromatic runs less painfull and sharper sounding, which leads to the answer to your question"
Why are country pickers/chicken pickers obsessed withy picks......well, because you get that sharper bassy tone on the low end that flesh on strings just cant duplicate.
And who wants to grow a thumbnail longer than your girl friends?