You can see the writing on the wall now, with stocks being pumped up around the world by central banks and with margin debt at an all time high.

The problem is, it could be years before there is a collapse, or it could be tomorrow. That's a lot of yield you might be losing out on. A near similar argument could be made in 2014. You probably could have doubled or tripled your money in that period.

And even if there is a correction, not all equities will decline significantly (some will stagnate, or just decline a few percentage points, some will still double), whereas others will lose 80% of their value.