Maybe not every academy does this, but in our gym people bow when they get on and off the mat. It may seem silly to many, especially to beginners, but there really is a point and purpose behind the action.
It shows respect: respect for your academy, the sport, and your fellow teammates for taking the time to train with you that day. Bowing also shows gratitude for the same things. You are giving your thanks for being able to get on the mat and training that day, for having a place to train in the first place and partners to train with that day, for helping you improve and get one step closer to the next level of mastery.
How about you guys? Do you bow on and off the mat? Let me know- otherwise, have a great day!