It's incentivized by the system. You get grants, clout, importance, job opportunities based on your publishing in major conferences. As of last year, the variance of review scores have been higher between reviewers on the same paper than between the same reviewer on different paper. So it's effectively become a coinflip. The best strategy when it's random is just to spam stuff.

Oh also at least 40% generated peer-reviews are contributing to this statistic.