Because, Dan, many feel certain arguments and claims are either not factually correct or are logically flawed. PDQ, for example, continues to ignore the fact that I and others HAVE agreed that some ownership of guns is BOTH allowed AND defensible. And your own reasoning about sports cars is 'correct', but irrelevant. Sports cars have other purposes than going very fast.... and their uses on highways is much more watched and regulated than guns are. One can have their license to drive revoked for a few speeding tickets.... and 'usually', speeding does not kill anyone, whereas firing a weapon outside a legal range is often/usually done with the purpose of injuring others!

OF COURSE weapons at home can and should be 'secured', but you KNOW how often they aren't! Those who insist they should be allowed firearms for 'self-defense in the home usually feel that a gun is of little use if they have to unlock a case or closet and load it before 'defending' their home.
There is not enough space on the newspaper's front page for the weekly stories of kids who knew where Dad...(or, sadly, Mom) keeps their guns! A few years ago, my ex-neighbor across the street bragged to me that he had a gun 'available' in every room of the house. He had two girls living at home at that time...under 12.

I will repeat this as long as others keep claiming that 'safety and enforcement' are all that are required.
"As long as a wide range of firearms are allowed to be kept in the home by average citizens, there will continue to be tragedies following burglaries and kids getting a hold of them!"
You simply cannot base the rules and logic on what YOUR abilities and practices tells you are reasonable. YOU will take care....too many others will not!