Maybe because their city's built on it. Not only is the river lousy with "beach bars" in the summer, not only is surf music hip, but Berlin also hosts an annual sand-castle contest, right next to Lehrter Bahnhof:
That is really cool! The snail/squid thing (I know there's a name for it...) is fantastic. Are there different faces around the top, too? Apparently when you get your sand imported you get serious about it.