While you can avoid some businesses, the need to enter some establishments may be necessary, and may even preclude carrying illegally, such as government buildings with magnetometers. Also, many of us are employed for companies that do not recognize the right to carry a firearm for personal protection.
So is the choice that we either leave a gun in our vehicle on occasion, or abdicate our right to carry altogether for any trip that might lead us to a "gun free" zone? Sometimes that is the choice, and we hope that we are not the unfortunate victim of an auto burglary. One thing you can do is to make yourself ugly to auto burglars. Do not have gobs of expensive stereo equipment, or leave items of value in plain view. The same way you conceal your firearm, you should also conceal your purse/laptop bag/cell phone/bucket of spare change. Make the interior or your vehicle a barren wasteland that isn't worth the risk to a criminal. And if you can't do that, then don't also leave a gun in the car.
I really like the idea of console vaults and truck vaults. A handgun safe fixed in your trunk might also work well. The financial cost would be burdensome to many, but the an illegal gun on the street can result in the ultimate cost.
I don't make jokes, I just watch the government and report the facts. -Will Rogers
An appeaser is one who feeds a crocodile, hoping it will eat him last. -Winston Churchill