My theory is that a lot of bassists are converted guitarists who find it easy to play bass with a pick but often struggle to learn to play fingerstyle. In contrast, those of us who started on bass -- "real" bassists -- almost always start out learning fingerstyle (and later struggle to learn to use a pick). So, I think converted guitarists sometimes feel like using a pick on bass is "cheating," since "real" bassists use fingers.
Personally, I played fingerstyle exclusively for 15 years, occasionally trying to learn to use a pick but always giving up in frustration. Eventually I decided to really commit to it. It took a long time for me to get to the point of being equally comfortable either way, and now I go about half-and-half depending on the song or, more often, my mood at the moment.