Because the Celts were not apt to build cities and instead revere trees, and because they treated their womenfolk with a slim degree more of social freedom than the Romans, they have become a convenient facade for those looking for an "other" to perceived patriarchal, industrialized Western civilization. I've met more than one Green Party activist who builds up the Celts as the original eco-feminists. An entire pseudo-religion grossly misnamed as Celtic has grown up around it.
Or at least that is how it is over here in the states. Those of you closer to Celtic countries have probably seen the other version of the Celtophile - those who believe in the Celts as a long lost golden race, which is then used to justify modern nationalism in Celtic countries.
This has always been my line as well.
(Well, unless we're talking about Greek philosophy. I'd rather smear rancid butter in my hair and revere an oak tree than read Plato).