Two are, one isn't due to old age, by the time I could afford to insure him after a break due to finances, he was too old to make that viable.
Despite the fact we won't do anything invasive or treat catastrophic stuff, the little sod has cost me the better part of 1K this month, just in adding up blood tests, consults, xray and ultrasounds to find out why hes hot, flat and miserable. (He is fine now... on steroids but not on them he is distinctly not fine so 1K later we still don't actually know what is wrong).
So yes, generally I would insure - one of the others managed to rack up 3K in a matter of hours a few years back at a time when I certainly could not have put my hands on that at a moments notice.
Keep in mind too, out of hours vets fees, and almost all are now at an out of hours specialist company NOT your own vet, can be £300 for walking through the door and they will not treat your pet (even if they cover your vets OOH) without payment up front.
Something as simple as cleaning out a wound and stitching a layer of muscle and skin (ok not SUPER simple but not actually ground breaking cutting edge veterinary stuff) was quoted to me as £1600, that is on top of the walk through the door and the £50 to do the admin to submit claim to insurance (had he had any, he also, did not).
We waited the 7 hours for our vets to open, with me holding a pad on his leg to stop the bleeding. And that still cost me £300 for the OOH consult (which did assure me he would not bleed out, which is why I went there as that is what I feared).
My own vet fixed it for a further £280. Instead of £1600.
If you have access to a credit card you can pay off, and a few K in the bank, then yes - if you do not, then no, I'd get insurance.
Also remember that insurance includes public liability - if your dog causes an accident or injures someone, or their dog, that could cost you ££££ to £££££££.