Could someone help me understand why this matters? Why worry about events centuries past when there's so much to worry about in the future?
To answer your question straight, the reason the return of the Parthenon marbles matters, is morality. [4]
One cannot appreciate the significance of such creations to the fullest when they are taken out of context.
[1] http://www.parthenonuk.com/ [2] http://www.parthenoninternational.org/ [3] http://www.marblesreunited.org.uk/ [4] http://www.forbes.com/sites/realspin/2014/12/23/the-british-...
It's about making sure that our civilization's treasures are protected and not ruined.