@Glennn,
I can think of many reasons where expanded background checks are necessary.
People prone to self harm and harming others.
People with violent criminal records.
Spousal abuse.
Criminal threatening
Association with known terrorists
Drug offenders
Documented drug addicts
Underage children without adult consent
Illegal guns sales from shows guns passing hands without background checks.
Guns inherited from dead relatives
Guns owned by military personnel who are no longer in combat but who may suffer from PTSD. (to prevent harming themselves)
Adolescents in dysfunctional homes.
Parents who neglect gun safety.
Republicans...
This is just off the top of my head and why you can't even think of one reason speaks volumes.