Recap episodes are pretty common in anime. Every so often there will be an episode (or multiple episodes like in One Piece) that brings the audience up to speed on presumably a lot of material. In the past few years I've noticed that even 1 cour anime will have a recap episode somewhere in the middle (between episodes 4 - 6), and recently there have even been shows that are 1 cour with 2 recap episodes(thought the title escapes me at the moment).
I've never seen a positive fan reaction to a recap episode, so why are they still so common? Are they a hold over from the days before Video on Demand (VoD) through The Internets? Or is it just another filler-related solution?
Recap episodes are different than recap OVAs for the purpose of this question.