That's not limited to Lemmy. It's what happens across all social media. A tiny percentage of people will post, a larger percentage will comment, and the vast majority will lurk. The general numbers I've heard thrown around are 1-9-90, but the posters and commenters are probably much lower than 1% and 9%. Especially as platform size increases.

As for why, and this is hazarding a guess: posting takes effort, commenting takes less, and lurking takes the least.

I don’t think the ratio is that far off from reddit. Getting involved takes effort. Up votes take none

I lost count of the times I started typing a post or comment and either couldn't come up with the right phrasing to convey what I want, or just decided that my dumb comment wasn't worth posting.

I think most people treat it as a news/content aggregator service...

Much of the time the perfect comment has also already been made.

It is easier to read than to type

What makes you think they do that?

That's just who I am. A lurker by nature. A browser in the night. I'm... Lurkman?

yes