Purpose of having door on every level of HDB multistory car park?

I could not understand the purpose of having door on every level of HDB multistory car park. Is it for security or for fire safety or just because there is a door way hence you need to have a door there? For users of the multistory car park, it is an inconvenient to have these doors especially when the users are carrying bulky stuff with both hands. Could we reconsider the need to install such doors in car park?