They already do have fund for backing these stuff up. Not only Binance, I believe most of the exchanges have a separate fund for facing unnecessary stuff like this. Business too follow the same strategy for avoiding unknown risk in the future.
There's a huge difference between keeping a separate fund and having an insurance.
A separate fund means the exchange will pay all(*) the missing money.
Insurance means the insurer pays for all(*) the missing money.
(*) It's actually not all the money, the upper limit is the size of the fund or the size of what the insurer covers.
However, this may be the best (or maybe the only available) solution. Let's read more:
i think the trading exchange should consider an insurance policy to cover loss in case of funds theft.
Do you think this idea with work in the cryptocurrency business?
First of all, there may be few (if any!) insurers that have the knowledge and the willingness to insure a cryptocurrency exchange. It's quite a complex business...
If the number of insurers is 0, clearly insurance cannot be done. If the number of insurers is small, the insurance may be expensive. If the insurance is expensive, an exchange that plans to stay on market for many years may find the fund @RapTarX mentioned be a cheaper option.
And there's something else: cryptocurrency exchanges may not like 3rd party audit (which and insurer may require) since exchanges probably do things that they shouldn't. One example is the new wash trading accusations against Binance.
So @RapTarX answer is not bad, just insufficiently explained.