Well, it turns out there are answers.
According to CBBC’s Newsround, which is owned by BBC (who make Doctor Who), it wasn’t designed that way.
“The Doctor’s TARDIS has a broken ‘Chameleon circuit’ which is supposed to enable it to disguise itself to blend into any environment,” they explained.
“For example in ancient Rome, it might look like a Roman pillar or statue from the outside,” they added (that would make so much more sense).
“However in the first ever episode ‘An Unearthly Child’, we discover that the circuit is broken and the TARDIS is stuck in the shape of a police box.”
While we have you, it seems some scientists think the TARDIS would have to contain a wormhole to be so much bigger on the inside than it is on the outside.
J.J. Eldridge, an astrophysicist at the University of Auckland in New Zealand, told Science News Explores: “If you wanted to make a TARDIS in our space, you would take a wormhole and curve your spacetime out to somewhere else to where you’ve stored the TARDIS.”
Mika McKinnon, a physicist who ensures TV shows and movies get their science right, asks why we should stop at one wormhole ― “I think it’s more fun to think of [the TARDIS] as a series of looped portals,” she said.
All that for its shapeshifting function to be broken by a single wire? Typical…