It's a fairly controlled bet with relatively little downside (companies are likely to cover a large drop in RSU value) and a lot of upside. Since the vesting window is 4 years, you can sell as soon as things best, you still get a salary and you can switch jobs at any time the risk isn't that high. And since you can make up a decade of regular income in a few years the logical approach is to roll dice when younger if you can.