I think what it really comes down to is that no one technique is truly "necessary". I mean, I know plenty of guys that do killer funk without slapping and popping. I know plenty of people that use picks for things that are usually looked at as finger tech. and vice-versa.
I think what it all really comes down to is what works for you. I mean, there are lots of bass players that I admire, but would never try to emulate their playing technique because it's not comfortable for me as a player. Using a 3 finger technique does allow for some really well done and very fast basslines, but some people can do it just as weel and are mor comfortable using just 2 fingers. Just my opinion.
