address – Why do bitcoin: URLs not use “//”, breaking “clickability”?

I want to have something like this in a plaintext e-mail:

Pay directly: bitcoin:addresshere?amount=0.001&label=Blablabla&message=Blablabla

But if I do that, it won’t be “clickable”, because the standard URL format would be:

Pay directly: bitcoin://addresshere?amount=0.001&label=Blablabla&message=Blablabla

Why does the bitcoin: URL scheme not use the // part? Is it intentional to not be clickable? Or am I wrong in my assumption that e-mail clients will not make it “clickable”?