Personal choice thing...
No different from your home/renters/car/life/etc insurance, etc.
A 'just in case' thing...
For a used vehicle, I'd seriously consider it. Depends on the year, miles, condition, etc.
Bought a Mazda B2500 (a Ford Ranger) used from the credit union, and they offered a bumper to bumper insurance policy for $500.00 bucks.
Two years later, the AC went out and the bill was $1,200.00 bucks, and they paid it 100%
If nothing happens and don't use it, then they made money, and am not bummed by it, as they took a risk on my vehicle...