So why don't pollsters regularly ask which political party is closer to voters' views on guns?

I have often wondered why pollster don't regularly ask this question: Which party is closer to you on gun control?  It turns out that The Economist/YouGov poll did ask this question for a while during 2010.  Does the double digit lead that Republicans have over Democrats on this issue explain why gun control isn't included when pollsters ask about everything else from the economy to health care to foreign policy.  Here are the results that I found for 2010.

10/23-26/2010 Gun control  Democrats 28% - Republicans 42% - Both the same 9% - Not sure 22%

10/2-5/2010 Gun control  Democrats 27% - Republicans 42% - Both the same 9% - Not sure 22%

9/11-14/2010 Gun control  Democrats 27% - Republicans 39% - Both the same 10% - Not sure 24%

8/7-10/2010 Gun control  Democrats 27% - Republicans 37% - Both the same 10% - Not sure 26%

The Economist/YouGov polls from other points in time is available here.