It's like this: the central character, Arthur Dent, has his home
destroyed, by the forces of order. And planet Earth gets bulldozed
too.
So, Earth being the home planet, the whole thing gets kicked off by a
sense of the loss of home. Like that.
(No pun intended, by me anyway: ) 'Loss of home' leads to a sort of
alienation. It propels the series, to a great extent.
That's about it.
(You mean you were expecting a long, serious, scholarly spiel? like
mentioning the eco-fragility consciousness thing subequent to Rachel Carson's
'Silent Spring', Jungian vs. Freudian, etc., etc. - ? You looked in the
wrong place, that's all; read the books themselves, if you want a big block of
Meaningful Content.)