The benefit of using a pick is a louder attack, which is really important when you're purely unamplified and near other, often louder instruments, and where the attack of the note is crucial. Dobro and banjo players are really top ones here, and I understand it's big for pedal steel players.
Classical and flamenco players pick with fingernails, but nylon strings are easier on fingernails than steel strings. I've heard fingerstyle players talk about superglueing slivers of ping pong balls to their fingernails to have something replaceable and more able to withstand the strings, yet more stable on the finger than fingerpicks.
There are players who just use a thumbpick. Nils Lofgren plays rock with a thumbpick and fingers. With electrical playing, especially rock playing, it seems like the benefits of fingerpicks are not more easily handled by amplification. For hybrid playing, picks are allowed but not necessary.