If we say something is going to be done around this time, and it's not, that impacts other people's real work. This is a core truth that I often struggle to get engineers to engage with. When we say that dates matter, they picture mustache-twisting managers inventing arbitrary deadlines. That does happen sometimes. But it's not at all the norm. The norm is running a business where your work isn't the only work that matters. Coordinating all these activities requires people to commit to dates.