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Going even further, deadlines are often a tool for signaling "the organization is trying really hard to achieve this fast". The shorter the deadline (as long as it's at least somewhat in theory plausible), the harder you're trying. Often most people involved (even those deciding on the date for the deadline) know from the very start that the deadline will almost certainly be missed.

I regularly see two kinds of deadlines. "Planning deadlines" describe an estimate when something will be done. "Signalling deadlines" signal priorities and motivation to employees or clients. Sometimes both exist in parallel for the same task and there is a subset of people who know both.