How many doors does your studio have? Possibly two, one between the control room and the recording area, and another directly out of the recording area for reasons of fire safety. (Bear in mind that if you carry out professional work in your studio, then in many jurisdictions a whole new book of fire safety regulations applies.)
Most doors in normal everyday life use a latch mechanism to keep them closed. So it wouldn't be unusual to see a similar mechanism in a studio door.
However, having a latch causes a certain amount of inconvenience. Whenever anyone uses the door, the latch makes a noise. In fact it makes two noises, one when the door is opened and another when it is closed. Yes you can open and close the door very carefully, but does every musician and singer who visits your studio have to be instructed in how to use a door? And will they remember?
This problem was solved way back in 1962 by the BBC (British Broadcasting Corporation - which probably operates more studios than any other single organization in the entire world). The solution was to having a spring closing mechanism, supplemented by a magnetic strip to provide an airtight acoustic seal. No latch is necessary.
Anyone working in a BBC studio can enter and leave the control room (which they traditionally call a 'cubicle') or recording area completely silently, without the risk of latching noises being broadcast to the nation.
This may be a comparatively small point in the whole universe of recording studio design and operation. But if people can come and go in complete silence, it will surely allow your sessions to run much more smoothly.
By the way... The door in the photo - it's at the BBC!
Great home recording starts with a great home recording studio. It doesn't need to be expensive if you know how to select the right equipment for your needs.