I think it depends on what kind of sound you're after; some bass tones can only be achieved with fingers, and others with a pick. I personally use fingers a lot, but that is because I usually play jazz, funk, and rock. But if I want to sound a little bit more aggressive I might use a pick, which gives a lot of more edge to the tone. I also like muting the strings and using a pick to get a 'James Jamerson' muffled sound with almost no sustain. A similar sound can be achieved by placing a sponge under the strings and playing fingerstyle like Jamerson did, but I like the extra attack the pick adds to the tone. I don't know why playing with a pick is frowned upon by so many bass players- it's a tone you could not get otherwise, and it works great in some instances where fingerstyle would not have gotten the right bass tone for the music. Ultimately, there is no right or wrong answer; you don't have to play with a pick if you don't want to, just as you don't have to play slap bass if you don't want to. Well, unless you're a session musician- in that case, you should definitely know how to play both.
updated by @pauljones: 22 Apr 2018 21:52:55