Anime isn't a goldmine as a business. It's only decent for the likes of Ghibli, but regular run of the mill produces are struggling to stay afloat at all. If 4k and HDR raised the costs, the studios wouldn't want to go there unless they have to. Ironically the move from physical media toward streaming would also lessen the need. Streaming quality is shitty in the vast majority of cases compared to the plain old BD, let alone the Ultra HD BD.