I hear what you are saying.
Some time back I used to work in private equity for SME's. Had to spend a lot of time reviewing peoples business plans. Average size funding was GBP 250,000 with exit in three to five years. For start ups, rather than turnaround businesses.
Now, even though many of the businesses plans were scrutinized and the investors carried out their due diligence unfortunately not all businesses made it passed Muster.
Business is risk, just like trading is risk. Black Swans do not only swim around the trading environment, they are everywhere. That's life.
The issues is WHEN a Black Swan may appear rather than if. If it is at the start than Bugger! If you borrowed GBP 50,000 and traded it to GBP 500,000 and the black swan knocks you down to GBP 150,000.00
There are trading risks and business risks, many businesses borrow or are backed by investors and fail, also many succeed because they were adequately funded in the first place.
One of the major reasons why traders fail is there are not adequately funded, so they take on too much risk and are over leveraged.
So Yes there are RISKs in borrowing money to trade, but there are major rewards being properly capitalised for the task, provided the trader has earned their spurs with a decent track record. IMHO.