My insurance policy (renters or homeowners) covers bike theft. Yes, there is a $1k deductible, but my bikes range from $3-5k each. Is this not a thing in the UK/EU?
If you want to to insure against bike theft, you need a separate form of bike insurance. They generally have no deductible, though.
But it's usually not worth the effort. Daily-use bikes are too cheap to worry about, and expensive racing bikes / mountain bikes never leave your line of sight while outside your home.