The theory being that it will revert to more manual, hands on moderation, rather than automated and more sweeping (eg. instantly banning people for simply posting in an unrelated but disfavored sub).
Reddit admin and users have no idea how much free labour they are benefitting from and how much subreddit quality will decline with this move.
Even things like porn subreddits will instantly be hit. There are bots that evaluate every submission and compare them against illegal content to instantly remove those posts. Without those bots, subreddits will get closed as they lose control over submitted content and bring the ire of admin and public media.
Although, it goes against the dismissive post to which I was replying, that said Reddit will provide all the missing functionality without a problem.