The cabins in the BA 747 fleet are tired as are the airframes.
Hire cars are restricted to 15000 miles.
Some are some aren't. Most of the B744s have been through a New First product refresh, the ones that didn't get it are retiring. I think a B744 needs to work a little harder to pay for itself than a hire car.
BA are running an old fleet like a lot of the flag carriers.
Airbus A318 2 3.8 years On 19 airlines operating this type of aircraft British Airways ranks 5
Airbus A319 44 11.4 years On 129 airlines operating this type of aircraft British Airways ranks 109
Airbus A320 47 7.7 years On 229 airlines operating this type of aircraft British Airways ranks 110
Airbus A321 18 7.6 years On 65 airlines operating this type of aircraft British Airways ranks 25
Boeing 737 19 20.7 years On 272 airlines operating this type of aircraft British Airways ranks 93
Boeing 747 52 18.4 years On 92 airlines operating this type of aircraft British Airways ranks 39
Boeing 767 21 20.2 years On 97 airlines operating this type of aircraft British Airways ranks 61
Boeing 777 52 12.2 years On 64 airlines operating this type of aircraft British Airways ranks 53
TOTAL 255 13.4 years The calculation of the fleet age can be approximated because it is only based on the supported aircraft
Fleet age British Airways | Airfleets aviation
It's only old compared to exceptional cases like Singapore and QATAR. Even Cathay fly some pretty legacy wide bodies having the first build B777s and A330s. The B767s are an issue as they're supposed to be well on their way out as the B787s are late.