I agree with you if you already have high assets and a high income no reason to take any debt.  If you don't have anything sometimes you might have to take
some risk and debt especially if you want to open a business.

Most people who start a business when they are young have no choice but to borrow from friends and relatives.  Small amounts maybe like 30k for a small business.  If you need larger amounts then you would need investors. 

I have been an investor in businesses before and I have run business for other people with P&L responsibility.  My observation why people fail is because people open a business which they are not familiar with.  Those which I have seen successful consist of people who have already about 8 to 15 years experience in a similar industry, Sales and mkt experience, P&L responsibility and people management skills.

As most people do not have the relevant skills it is not surprising 90% of businesses fail.

If you do have the experience then it makes sense to borrow as normally you wouldn't open the business unless you already had a contract to sustain your cashflow but you only need to borrow after you get the contract as a bridging loan to perhaps run the project as distributors will not give you 100% credit the first time you do business with them even if they have been friends with you for like 20 years.