One of the common argument of the pro-gun crowd is that gun control doesn't work because criminals who would fail background checks still manage to get guns...e.g. they get them from friends or they still them from houses. Or to say "the criminals will easily get guns, while those law abiding citizens will find it hard time getting guns to protect themselves."
Gun storage laws (and smart gun laws if the NRA would allow them) are designed specifically to address that.
If gun storage laws only lead to a 1% reduction in gun deaths, (mostly via suicide via dad's gun), then they are totally worth it. I'm sure the effectiveness is a bit higher than that.