Last time I got car insurance (a year ago?) I believe they still asked if it had an alarm, implying they still give a discount for it. Do insurance companies think it actually matters? Or do they just get kickbacks from alarm companies?
Although in practice they are money making companies, and likely use statistics to find ways to upsell you.
So once upon a time car alarms were rarer, and they could charge more if you didn't have one.