Future proofing, at some point I will go 2.5gb sync or higher on my Internet pipe, the connection I think can go 10gb sync with some upgrades to the local exchange.
Also because I can, and almost everything else I own for my back haul already has 10gb ports and the bandwidth to support it including my router and all my switches.
Do I need it? Absolutely not, its just fun to do and the only reason I haven't done so yet is cost of suitable hardware.