I've seen that these estimates are inevitably used to judge the performance of teams and individual contributors. If you ask why developers put up with this, my answer is that it's not done openly or transparently. Yet I see it happen, and it is at times acknowledged in hushed tones among insiders. No one's explicitly being promoted or awarded bonuses based on their ability to meet ticket estimates or anything like that. However, a team's failure to achieve predictable burn-downs will be used to justify intervention, and an employee's failure to sustain a certain velocity will be used as part of firing decisions. It's a pulse for management to watch and leverage when needed.