I suspect it's a legal minefield and much easier said, than done.
'EU Law' doesn't make all of the countries that make up the EU one homogenous blob where everything needs to work the same.
EU Law provides many broad directives on how things should work in general, but the detail is country specific, and it's almost certainly compliance with all of the details that have meant that Kickstarter have decided to start with just the UK at first.
They'll probably start to provide Kickstarter for residents of other EU countries along the line in the future.