And because it's so easy for everything to be a subscription now, most of them are of negative value to the subscriber. That is, the subscriber gets nothing useful from the email subscription and has to deal with the useless emails taking up decision space (do I delete it now? what if there is something valuable inside? maybe I save it for someday because I might use that coupon?) when they come in.

In other words, they are clutter, or litter.