The other thing to consider is third party liability cover.Imagine if your dog got out caused a car crash which resulted in a claim for personal injury and property damage resulting in a huge claim against you. "food for thought".
The third party liability is basically the sole reason we have insurance on Diesel; he's a grumpy old sod (and over 10, now, which makes him expensive to insure - many insurers won't start new insurance on a dog already over 10) and has taken a distinct disliking to a couple of larger dogs in the park. He's never let off the lead in the park now, for that reason, but I'd rather have the liability insurance there
just in case he breaks his lead/escapes the garden and does an injury to someone or something.
After all, you are personally responsible for the actions of your dog, legally speaking (unlike cats, which are so much easier .. and shit in someone elses garden usually

).
He's had a couple of run-ins with the vets and we've not claimed yet as it's always been below the deductible or whatever they call it :/