Because, no. Great show, but he looks just as unattractive after watching the series as he seemed before.
In certain, posed, controlled photo shoots, he's attractive. He was also very cute in the series "Fortysomething". It's on netflix and youtube if you care to check it out.
However, in Sherlock and most photography he's really weird looking.
I love him and think he's hot. But it's the whole package that makes him hot for me. Sometimes he looks like he doesn't have a chin. It just disappears into his neck.
If the "whole package" completely excludes the way he looks, then... Well, at least he's got a British accent going for him? Sorry, I do.not.see.it. He's the opposite of hot to me.