Because it's such a minor issue.
The Morris worm infected 2-3 orders of magnitude fewer computers...
Put another way, as dreadful as it is, Superfish was never at risk of partitioning the internet. The harm is restricted to those luckless individuals who purchased a Lenovo laptop in the particular time frame at issue; quite possibly a crime, but not, playing devil's advocate for reluctant prosecutors, a 'something must be seen to be done or I'll be lynched' level crime.
Whatever would happen in that situation should happen here. I would guess prison time would be involved.