My car, well that I can't afford to replace if I total it. So I do insure that for £500 a year. I think my car would be about £5k so that assumes in going to total a car once every ten years. Insurance company is still winning... But probably not quite as much as on the bike.
car insurance you need because, well, you have to have it.
but unless you have a really expensive car, the main point of the insurance is not to cover your rust bucket, but to pay for all the damage you might cause in an accident (you might hit a really expensive car).
that being said, you are right. you should get insurance for costs you don't want to bear. in this case, i don't really think theft is big issue (at least for us it isn't, we don't have a lot of easy to carry items worth a lot). it's the fire and flood. for example, if you have a lot of specialized books, you could easily have a huge amount just in books.
but back to your point about insurance and cost, I think many people over insure. for example, i think insurance for a smartphone is in that category.
but the OP said she got a quote for 65 a year? unless you really don't own much, that sounds really good.