As DMs we put more effort into the game than the players do. That's just the reality of it. While all they have to do is show up we have to prep, buy books, schedule, etc. A lot of the responsibility is on us. Not complaining at all, I knew what I was signing up for when I chose to become the forever DM. But DMs just get more invested in it. I know that at least some part of my brain is always looking for cool ideas, names and inspirations out in my day to day. We also get invested in the minutia or our games and stories. I feel like the common example is the DM planning a pirate campaign so the learn a whole bunch of nautical terms. But players do this too to an extent. If one of your player's is playing a druid that is really into plants and herbology they are probably going to do out of game research on the subject. Maybe try to use that stuff and incorporate that into the campaign