Black tubes running under a Delta faucet?

[Mike Lamb]

I did some research and the black tubes are apparently water lines for the faucet but I already see water lines running up into the bottom of the fixture. So i'm confused.

[Bill Kibbel]

Those are connector tubes for wide-set handle faucets. 

Water supply is connected separately to the hot and the cold faucet handles like any faucet.  When a valve is opened, the tubing delivers the water to the W-connector.  The tubing from the middle of the W supplies the spout.