Because there are considerations other than how to solve the problem in the debate. For one, that solution is completely in opposition to the 2nd Amendment which is not going anywhere making it a moot point. I would like to see solutions which greatly contribute to the overall safety of citizens without infringing upon the Constitutional rights beyond what is included in a wholesale ban.

For example, it has been reported that the husband and wife who committed the crimes in San Bernardino were on the no-fly list. Why is someone who is not allowed to fly because they are suspected of being a terrorist still allowed to purchase a firearm? Closing that loophole seems prudent.

Dylan Roof was allowed to buy a firearm despite having been arrested within a few days of the shooting incident. He was allowed to purchase the gun because the FBI didn't get back to the retailer within 3 days of the background check being completed. Making sure that the FBI is equipped to handle purchase applications in a timely manner seems very prudent.

The Virginia Tech shooter used 10 round magazines that were compliant with the California Assault Weapons reforms as did the shooters in the Columbine shootings. They just brought more of them. This therefore seems a silly ban which only infringes on legal users for no actual purpose.

Closing straw purchase loopholes seems like an obvious step.

Closing individual sales being exempt from federal background checks seems like an obvious step.

There are many things which could greatly contribute to the safety and peace of a majority of citizens which do not infringe on the Constitutional rights of legal gun owners. These are the kinds of things which we should be discussing.