For a one-shot I played on Saturday of Cyberpunk Red*, I read the entire rulebook, with an especial focus on any world-building and history sections. I've never met another player who does that sort of thing unprompted. The most I've seen is mechanically minded folk doing the research to make an at least somewhat optimized character, because that's key to their fun and not easy at the table.
For my tables, I know the reason. I'm the person who's excited to run the game, and put in the effort to learn and assemble it. The players are excited to play, but without me, they would never spend their free time building characters, reading forums/subreddits, or finding new systems of interest. The game play at the table is already an investment above and beyond what they would do on their own.
Now, I've had luck getting outside of session work and responses, but I know that I need to ask them repeatedly, usually once in person and twice in-between sessions to get what I'm looking for. But, in remembering that I am asking them spend time and energy in a way that is for my benefit (even if I think they will as well), I'm...well, it's not that I'm not frustrated, but I do understand that it is no personal slight against me. They've already gone out of their way for me, if they're showing up for the game and are present and focused at the table.
So, I really try and limit what I ask of folks. Doing their leveling up in-between sessions, communicating with me if they're finding something missing/unfun, and the basics of scheduling. If I need to communicate something about the world or lore that it's important, then to get the best result, I need to find the way to deliver that information, in a interesting way, at the table. Reading dry text is something only weirdos like me love to do.
*WHAT AN ABSOLUTELY ABYSMALLY ARRANGED TEXT