In the case of blogging, writing is (typically) one's product. Writing is relatively cheap and depending on the subject is highly commoditized, so you need to write a lot to incentivize audiences to return and to continue to consume, and presumably pay you somehow.

This isn't always the case. You might be an otherwise famous individual who will have an audience regardless of your publishing frequency. But I think for most bloggers, you have to have enough material that people will visit, and continue to make more so people will come back.

I published between 1 and 3 times a year on my blog/website. But then I'm not doing it for income.