Reasons people are passive:
- People are destructive, especially self-destructive. Not doing much limits the destruction.
- People don't know what to do.
- People don't want to make the wrong choices, try not to choose.
- People don't want to be responsible for choosing stuff.
People broadly don't want to live. They don't want to do things, make choices, decide what happens – and maybe make mistakes and be responsible for some non-ideal outcomes. That's what life is. Acting and choosing. People don't like that. Passivity is their attempt to approximate death. It's their attempt to limit their lives.
Passivity is a choice and they're responsible for the consequences. There's no way to stop living besides actually dying. But being passive helps them minimize what actions they've clearly taken and what decisions they are clearly responsible for.
Like if I suggest we go to McDonalds and you say "OK" and then you have a bad time, you'll have an easier time lying to yourself that it isn't your fault. Your choice to say OK will seem different to you than leading the way. It's still your fucking life. You're still deciding what to do with your time. But you'd rather have someone else to (falsely) blame for your suffering than suffer less. So you avoid the sorts of situations where you'd be clearly responsible for problems. You avoid leading and being first and wait around for someone to tell you what to do, or even just make suggestions you can obey.