If today you want to insure your car against theft, you must have an alarm fitted. It makes no difference what kind of car you have, even if it's a 1940 Silver Ghost, it must be drilled, cabled and fitted with an alarm because Insurance Companies insist that car alarms work as a deterrent to car thieves, and assist in apprehension of the culprits in the event that the alarm was not quite deterrenty enough. Which is a bit like saying this body armour will stop bullets, but even if it doesn't it'll keep enough of your body in one piece that they'll be able to tell who you were.
They're completely and wholly wrong, though. Car alarms, and house alarms are just one more example of how the human race can make itself fucking miserable through no force more powerful than lethargy.
Car alarms achieve only two things;
That's it. No one ever, not at any single point in history has ever so much as looked out of the window to see if the piercing whining screech is someone nicking someone else's car. The most you might get is someone looking to see if it's a car of someone they know, and then only to discover that they can the next time they see the person in question punch them squarely in the face for being a cunt (for not bothering to tweak the sensitivity of the alarm so it goes off when, for example, someone puts a piece of scaffolding through the passenger window, rather than because a moth has alighted on the aeriel). In that rare case, then you'd positively encourage the car thieves and that's perhaps the thing, because if a car is stolen, then one thing you can be fairly sure of is that it's car alarm will be taken away from wherever you are to somewhere where you're not, probably a council estate. That's a good thing. So it stands to reason that car alarms actually make it easier to steal cars as by driving them away you've endearing yourself to half a county at the same time.
It's not even like they assist the Police with working out if the car has been stolen. Whilst the Police are getting possibly younger and absolutely shorter, even they can still tell that the car driving at breakneck speed with scant regard for common sense is probably in need of a little stopping, and maybe some condescending questioning, so what difference does it make if it's also got an alarm going off? Bugger all, I reckon.
Even then, if the Police do manage to stop the twelve year old who nicked it, they get told off by a juvenile judge (either way that works) but then told how special and clever they are by social workers who seem to think that this will help. This of course is wrong because all children are stupid. That's why we don't let them vote, drive, work in nuclear power stations, join the army, perform open heart surgery or make any decision whatsoever about their lives. Children work very much of the basis of pain avoidance - if you don't want them to do something it should be very clear to them that if they do the consequences will be painful in some way to them. Of course now you can't just hit them, despite tends of thousands of years of this being perfectly good enough, now you have to explain to them how their actions have consequences and wouldn't it be bad if these consequences happened to them instead? And these brainless yobs just hear a sound that has no meaning and the clear message that being a shit will get you stuff, and if you're a bad enough shit they'll send you on holiday to race carts as a character building excersize. Wierdly the rate of recidivism in children is about the same as the rate of child death. This could be interperated as meaning the best way to stop a twelve year old from stealing any other cars is to shoot them, but I'd never support such a scheme.
Instead I'll point out that after you have had your car stolen by children, in the unlikely event it is recovered intact by the Police you don't get it back - they keep it. As evidence. They put it in a giant zip-lock baggy and slap a label on it. Then you go to the insurance company to complain about your lack of a car and they say that your car isn't missing, it's just in the police station. Yes, it WAS stolen, and you were insured against that, but now it has been UNstolen and you're not insured against that. So you can't get a new car, they won't provide an alternative since your car is perfectly functional and so now you've had your car stolen and you've got to buy a whole new one, and get that insured against theft again, not to mention all of the things you have in your car that again you insured against theft, but upon which you cannot claim because they're not missing. So that laptop that is critical for work, and you'll have to replace because work won't pay for a new one, your entire driving music CD collection all all that crap in the boot that you keep meaning to take inside but never get around to, it all needs replacing, and all from your pocket.
But just try explaining why you don't want a car alarm to the chap selling you the new car, or that you will not be requiring theft insurance on it to a broker and just watch the total failure to comprehend cross their evil little faces.
But do we as a people think 'aha, these car alarm things really don't do anything useful, all they do is irritate people on a regular basis, we should remove the requirement to have them fitted, boost the rate of doing people for noise making for a little while and thus usher them into the past as a bad idea? No. No, we still suffer this intellectual lethargy, this weak minded assumption that car alarms MUST work because otherwise, why would we have them?
They DON'T WORK, and they NEVER HAVE.