Is there a difference? A system like Lavabit is meant to provide technical defences to legal threats. It has to be; that's the entire point. It's not like Levison was providing (or claiming to provide) any defences from any non-legal threats. What Levison needed to do was design a system which did not technically allow him to comply with the subpoenas he received.

And at least for American's, your counter about "can't the government just grab your laptop" is incorrect; you have a privacy interest in your laptop that you do not have in a 3rd party servers. You have stronger 4th Amendment protections, plus a 5th Amendment right not to incriminate yourself. (This last point gets confused; the government does have a right to compel you to give up your keys only if they already know what's being protected. If they know that you have a child porn on your laptop from other means, you must let them access the child porn on your laptop. If they have no idea what's on it, they cannot compel you to let them access it.)