Hacker News audience, developers or/and internet workers population in general are very sensitive to commercial newsletters. There are lots of comments that read "commercial newsletters = spam".
But reality is that for many online businesses email is the primary sales channel or a very important one. Lots of commercial newsletters are sent, but they main reason for this is because they work. Plain and simple. Lots of "normal" people (not too tech savy that will never hear about Hacker News in their whole lives) use commercial email as on their primary ways of ecommerce browsing. Just as setting up a beatiful and atractive front shop one hundred years ago made a difference in your bottom line, email is an element of crucial importance. Furthermore, lots of ecommerce companies have invested tons of money in developing this channel. Hey, maybe your salary is paid by one of this ecommerce giants! So three things:
1) Commercial email works. Many people don't bother receiving lots of commercial email. In fact, they love it. Google knows this, so:
2) one of the main reasons for Google making this change is to create an effective channel to deliver their own ad impressions in the format that people loves and use. But,
3) in doing so they may be invading a space in which lots of companies have invested a lot (and those same companies surely have already invested in other Google products).
Its a similar pattern with SERPs: you invested in SEO but now the first page is only made up of Google products or paid positions.