In California (and some other jurisdictions have similar rules), police cannot, by law make a warrantless arrest for a misdemeanor (with some specific exceptions, none of which is applicable to the pattern of offense at issue) unless the crime occurred in their presence, and prosecutors generally do not pursue misdemeanor warrants except in conjunction with broader investigations.
(If the offense occurs in the presence of a non-police witness, something that a casual observer would describe as a police arrest may occur after the witness reports to police, but that's actually a citizen’s arrest by the witness with police assistance. But a camera isn't a witness, and, as for police misdemeanor arrests, a citizens arrest for a misdemeanor also requires the offense to have occurred in the presence of the arresting party.)
What's the crime? Stealing something that is less than $1000? They could have stolen that from the front of a store and if they weren't detained by a store cop, the police won't do anything typically.
If they plead guilty, they probably would just get a small fine, not worth the time of a detective to make the case.
I'm describing the reality of the world we all live in. Even if its not their first time, they'll be out in a day or two, maybe not even that. Its just packages, most of them under $100, no one in harms way, no drugs, no guns/knives. Even if they broke down your door when you weren't home and went inside to steal your package, there's going to be no APB on their license number, no road blocks, no helicopter sent out to see where they are.
My time in retail quickly taught me that unless you catch and hold a perpetuator, nothing will happen to them.
"We have them on tape! I ran outside and wrote down their license plate?"
"What was stolen?"
"$250 worth of goods!"
"Meh, we know the guy, but if its under a grand the DA won't do anything. Since we know him, we'll tell him to avoid your store, if he does show up again and steals something, we can get him on trespass and stealing, the DA might do something then.
The fact is some people live 100% on small thefts, small odd jobs paid in cash, some begging. They'll be living with their parents at 30-40, with no assets in their name, borrowing cars to get around. There is no down side in swiping a few packages besides the pain in turning that into cash, which is the only disincentive to them stealing.
Serious question then... what's the deterrent? Sounds like a person could spend all day looking for packages, resell the contents, at the risk of just paying a small fee if one happens to prosecute...
Welcome to the reality. Typically, the criminals are caught with lots of items, and there's theft and possession of stolen property. Or if they are stopped, they are also carrying drugs and they'll get charged with that.
Edit: Also, its not so easy to sell a bunch of random things for the cash. For every iphone that might get you a 100 or so in one transaction, there's a bunch of random things that you might get you $20 if you spend a day trying sell them.
