Why insure
The risk of bad debts is real and the costs can be significant.
Bad debt is often cited as a factor in the total collapse of a business.

Debtor item
Many businesses will have over 40% of current assets in the debtor item on the balance sheet.
Other assets will probably be insured - what about receivables?

Concentration
Does your customer profile fit the '80/20' rule? Often the turnover from the top 20% (by number)
of customers makes up at least 80% of the total turnover. What would happen if a major customer failed?

Profit Margin
How much extra turnover would it take to replace the lost profit from one sizeable bad debt?