All of the companions you're not captured with are brought on via a quest they're personally involved with too. Whenever I replay the game it makes it easy for me to bring on and drop of people with those quests.
To me they feel like they sign-up as permanent members a little too easily whenever they join your party. To the point where, when the "...you should know, I'm seeking to rescue/revenge my sister/nemesis" dialogue shows up I feel like the PC has just rooked someone.
Also more banter in BG3 is a good thing, we get some stuff right now between SH and Lae'zel, and between them and Wyll, but after a while in BG1/2, half the reason to bring on characters is to listen to them bicker on the road. I'd like to see more in BG3.
