Lets take the Snowden case. He released tons of info regarding the US spying on it's own citizens, but how does that directly effect my life today? To put another way, how do I FEEL the day to day impact of these programs? The answer is simple, I don't.
I have no idea whether the NSA has a record of every website I have viewed. I have no idea if I have a file on some government server detailing my porn preferences based on my google searches. I don't know if the government knows of my relationship status based on listening in to my phone calls. Essentially, unless and until the government decides to use this information that they may (or may not) have to blackmail/arrest/detain/publicly humiliate me, it doesn't impact my life in a noticeable way
Now, lets compare that with the gun issue. When the federal/state/local government passes a gun law, if I am a gun owner I FEEL the impact of that law. If someone wants to buy an AR-15 and there is a threat of banning the weapon, that person feels the direct impact of the issue in his life. If someone wants to carry a concealed firearm in public (something completely legal in the vast majority of states, btw) but they live some place that does not permit it, they FEEL the impact of that law.
This is also why for people who don't own guns and have no interest in doing so, gun restrictions me nothing to them. Banning assault weapons have no negative impact on the lives of people who have no desire to own such firearms.
I am certainly not saying that the right to firearms is more important than the right to privacy from government surveillance. What I am saying is that it is FAR easier to find and organize people who have felt (or would feel) the real life impacts of gun restrictions, than those who have felt the impact of the NSA's surveillance program.