Why not dual audio?

I understand that most fans find Japanese audio much better than English dubs (as well as I for some anime) but there are some really good dubs out there that are worth watching so why not encode with dual audio?
I mean all it does is adds ~15-20MB to each ~130-150MB x265 1080p episode (hardly 500MB per 24ep season) but it would be complete and more fans will be able to watch it and I believe Hi10 is the only encoding group which can encode with such high efficiency in size while maintaining the quality.
So it's a kind request to all the encoders to consider dual audio encodings as most Hi10 encodes don't have that.