Denim's ability to last when your body hits pavement is measured in thousandths of a second. Assuming you only slide down the road, with no crushed bones or joints, you will only meet the nice people in the burn ward. There's a reason depictions of Hell are always burning.
A really good riding suit will run more than a thousand dollars; in some cases a whole lot more. Five minutes in the ER will cost more. Orthopedic surgeons and anesthesiologists live in multi-million dollar houses.
Think of it as part of the motorcycle....