The fact that people managed their lives without the benefit of a modern convenience at some point in the past is not a valid reason not to use that convenience today. After all, people got by fine (and some died early too) at some point in the past without:
-electricity
-automobiles.
-indoor plumbing & running water
-wired phones
-ambulances with defibrillators and recussitation drugs
-air-medevacs and trauma centers
-door locks
-home alarm systems.
-organised police services with cars and radios
Look at it this way: one way to measure risk is to define it as:
Risk from event = Probability of event x degree of harm from event.
Even if an event is low probability, if the degree of harm is very high, then the risk can be said to be high, and worth mitigating. Your child being abducted, sexually abused, then killed is a very high degree of harm. Even if the probability is very low, the risk is still significant and if a risk mitigation strategy is easily available, then it is worth adopting. On the other end of the spectrum, your child missing the buss, finishing practice early, or having their buddy who is to drive them home being too drunk/stoned to drive safely, are relatively high probability events, with relatively low degrees of harm, and therefore still risky enough to be worth mitigating.
And finally, I would wager that most folks would agree that the level of harmfull activities involving young teenagers has increased significantly in the last 20 to 30 years, specifically: degree of violence and proportion of violent incidents involving lethal weapons and minors, propagation of of drug and alcohol use in early teens, sexualization of early teens and sexual predation on youg teens and pre-teens. How did we deal with such events back then? The individual child involved did their best, hoped someone would see and call for help, and often wound up dead. Society went on, shook their heads, and tsk’d tsk’d. The individual kids and parents had a tragedy on their hands that, today, could possibly be averted. When it’s your kid, you don’t care about odds and probabilities, and rates changing. All you care about is that it not happen to your kid.
Twenty bucks a month seems like a reasonable cost to me…