The Doctor’s TARDIS is small on the outside. When it lands on someone or something, how does it know exactly where to place them on the inside?
Why doesn't it, for instance, place what it lands on at a random location inside?
If one considers the active control room as the "center" of the ship, as well as the most room where most of the important events are occurring, it's logical that any item landed on/around would appear there as a default.
IIRC, the first time something was landed on was Logopolis, where the TARDIS landed around what was assumed to be an ordinary Police box, for the purpose of taking many complex measurements. It wasn't ordinary, and it resulted in many complex configurations.
Having said that, I would assume that if the settings were changed, an item could be set to appear in any room or location. If it were a hostile alien, they could land the capsule so that they would appear in a locked room far away from the control room.