They do. Lots of the podcasts I listen to ask users to leave comments on their website. Some even read out the comments in subsequent episodes. But moderating

They do. Lots of the podcasts I listen to ask users to leave comments on their website. Some even read out the comments in subsequent episodes. But moderating comments - even on a niche post - is a chore. Wading through spam, trolls, arguments, etc isn't fun. It's much easier to ask commenters to email in - and that's what the majority seem to do.