The existing systems of an established business also increase the chances for success. Sales and marketing, accounting, inventory tracking, employee payroll and production systems are all in place. There may be some changes needed, but not all at once. In a start-up, all systems have to be in place on the first day. Along with the buyer, the seller, banker and vendor become partners in the business, each sharing some of the risk.
Every creditor feels more secure with an established business entity.
Most banks don't even finance new start-ups. Overall, there is less risk in purchasing a going business than in starting one, even if there are major areas which need improvement. Or the seller can indemnify the buyer. There are several ways to do this. The idea that there are operational liabilities that can't be easily changed is usually just wrong.