I definitely respect lurkers, and clearly they would appreciate being able to follow and filter. But, they can do so by requesting an invite and making an account. If they don't want to do that, this community doesn't lose anything — lurkers don't contribute.

Quality posts requires effort, why should one invest time in it, when there is only a limited amount of reputation to gain?

This is a separate concern you're bringing up, right? We do it for the fun of gaining levels and reputation, but mostly because it benefits the community. I don't think much of fake internet points, personally.