These background check bills seem to be sponsored by the “holier than thou” big dealer shops which do not like private sales or gifts. By crushing main street they are able to direct traffic to their government approved operations. They think they can stay in business by selling muskets.
They do realize that a thriving secondary market helps drive the primary market. Guns are, among other things, an investment. If the owner can't sell his investment, he's less likely to make the initial investment in the first place.
Also, people sometimes sell one firearm in order to fund buying another. That possibility goes away if there's no way to market the older one.