Well, if I wasn't clear enough: the fact that someone have used a tool for personal reasons and may recommend it as a good tool for work is not enough to justify spending on those personal use cases. You need this to be a healthy conversion funnel and valuable brand awareness channel, otherwise you are wasting money. To make a call you need data from marketing research and I would assume that Slack marketing team knows more about it than HN crowd, simply because they are in position to have this data and HN crowd is not. It can be the case that they are not acting professionally, but I would not assume unprofessional behavior by default.
someone hav[ing] used a tool for personal reasons and may recommend it as a good tool for work is not enough to justify spending on those personal use cases
I am sharing that I have an equal and opposite opinion, which is that the someone having used a tool for personal reasons and may recommend it as a good tool for work sometimes IS enough to justify spending on those personal use cases
You are right that data can inform the decision, of course, keeping in mind that the benefits include intangibles like goodwill, which goes further in the techie community than in a layman community imo
