That always seemed silly that you can’t do this.
You can have all the laws you want but if the DA does not charge then there is nothing you can do, even if arrested, the criminal walks free. And the police eventually stops investigating and making arrests for the crimes that the DA won't charge. And the DA will get re-elected because the voters, as stated above, have no clue, don't know who is the DA or what does he or she do.
Inducement generally means more than merely providing an opportunity. The officers have to try to persuade you to commit a crime.
Purposefully leaving valuables in an unlocked car and prosecuting anyone who took them would probably not be entrapment because normal law abiding people would not take those valuables. The police gave them an opportunity, but the criminal intent originated with the people who took the items.