In the case of BG1 the said background is what happens with the charname along with the mystery that surrounds him. It is particularly cool that you can experience all the story yourself both embracing his ancestry and writing your own story. No wonder for me why so many people being attracted to him. There’s no need to force any cause for their company, since the charname himself is a cause enough.
This is what BG3 lacks imo. Mainchar is bland and practically non existent. He resembles more of an observer, while the first roles belong to his companions.
You can criticize the BG3 MC if you want, but that's not what this topic is about. This topic is about the relationship between the MC and the companions. the OP claimed that the way the MC is built makes it hard to believe people will follow him.
I think it is a very common problem to crpgs, and was present in bg1 as well, regardless of how good the backstory is (and at least on the case of bg1, it's really good)
