Could they have held it? Possibly. But maybe if they held it, it would delay the first flight in the morning and someone on that flight would miss their connection. Maybe they were trying to get out on time to beat a crew timing out or weather. It's also a case that you didn't land until 13 minutes until departure, you have to be at the gate 15 minutes to departure, and not knowing if you could/would sprint, they had no idea how long it would be, so instead of delaying everybody else, get the flight out on time and rebook you for the next day.