Because there is nothing in this world that can match up to David Tennant's hair.
(Due to the massive number of Tumblrs referring to various Tennant body parts, I'll try to keep reblogging to a minimum and make fresh posts instead!)
Submit any Tennant Hair Porn you find here! Apart from the odd screencap, the material posted here is not my own. I get most of my screencaps from Sonic Biro.