Yes, you might waste five years (in your words) of income. But that is not a "risk".
A "risk" for me is "this could all go badly wrong". Not having an extra five years of savings is just a fairly straightforward consequence. It's predictably going to happen, I can decide if I want it.
Real risk is "something can go catastrophically wrong". If say you've taken out a huge bank loan to fund the business and you have to declare bankruptcy if it fails, now _that_ is a risk. But nearly every founder I've ever met has taken nothing like that risk.
That's my point, startups are not risky in that sense, for most people, most of the time. It's kinda strange that so many people think they are.