First, because of the tax advantages we just discussed in last blogpost.
Second, it is actually not a loan from your own money, it is a loan from the insurance company. It will use your policy's cash value as a collateral, therefore even with a loan, you will not see your cash value decrease, it will continue to grow tax-free. The only values that are reduced on the ledger when loans are taken are the surrender value and the death benefit, because the "lien" assessed against those two values.
Third, insurance carriers would charge an interest rate for the loan, but all the gains the insurance companies get from all the loans will be distributed back to the shareholders, this is very important because for whole life participating policies, the policy owners are also the shareholders of the insurance company!