Board Thread:The Reference Desk/@comment-6511852-20130302022313/@comment-7841417-20130405151242

Obviously it is a writing/costume thing, but for the sake of story lines perhaps there is some sort of perception field that the TARDIS emits sort of like how people who travel in the TARDIS even though they speak and hear English to the locals they are speaking the local tongue.

Basically though not explaining it saves time in having to invent something.

As previously mentioned by someone the earlier doctors 1, 2 and sometimes 3 would have their companions play dress-up even Doctor 4 did that later doctors it is usually just on rare occasions.