1. Imposes cost on people serving content even if they think the content doesn't need it in terms of machine resources.
2. Imposes an extra cost on people serving content, in the form of SSL certs. ("Why do I need to pay for this when I'm just hosting a plain vanilla homepage!?!?")
3. The PHK rant.
My point is, not everyone believes that every request should be encrypted (I do), and Google has face criticism on both sides of the fence from purists who believe HTTPS somehow takes away some of the original freedom and centralizes the Web a bit more by requiring cert-authorities.