re: Why?
Skylab wasn't, Compton wasn't, some Russian Salyuts weren't.
The HST is in orbit between 28 degrees north and south, a smaller fraction of the earth's population than the Russian orbits.
If it did hit the ground, chances of killing a person are extremely remote
but chances of recovering pieces are much higher and those pieces would have a great value .
There's the case of the woman who's car was hit by a meteorite and she got to sell her car for several times its value.
Raoul