They used to be inside of a house but they are regulated that they must be visually checked I think it is once a year or once every 2 years. (long time since I worked there) Meters used to get read 3 out of 4 quarters for urban areas, 2 out of 4 for rural areas. It can be hard to access properties when people aren't in and then sometimes harder if they are in the cupboard under the stairs with a million items in front of them.
They started putting them on the outside of houses at least 30 years ago. 2 reasons, one for meter reading and that visual check of meter tails and tampering issues (this is why the crimped metal wires have an engineer's code on so they can see if it has been tampered with) plus if you don't pay your gas or electric bill the utility company doesn't need to apply for a warrant to access their meter, break into your property and fit a prepayment meter. Plus they charge the customer for the warrant and tell you where to collect your keys from because they usually go in through the locks. And yes I used to work for a utility company. Have been involved in meter changes etc.
It is rare someone tampers with anything in the meter box.