As a player, in any sort of on-going game, I prefer to make a character with some kind of backstory.  Some ties to the world, some motivation to be an adventurer.  Some reason to be wherever things are starting from.  But I don't necessarily have to start off specifically tied to the adventure/campaign to come.
The DM & other players will come to know these background details.  I'll discuss it with the DM, & I'll type them up a few paragraphs.  They can use this info any way they see fit.  But if I get a response that indicates that they don't care & don't see the details of my character as being important?  Well then, I hope they aren't intending for me to care about their plot details....
The other players will learn these background details because I will talk about them in-character.  And just in general conversation.