If you took 10m of funding and exited for 100m your VCs will NOT be happy, they need you to hit it out of the park to balance out all the losers in their portfolio. Similarly, your engineers who are taking less-than-competitive wages should not be happy, your founders should not be happy. Everybody's interests should be aligned, and focused on getting spectacular returns, not simply good ones.
We're saying the same thing. It's either worth a TON of money, in very very rare cases, or it's really not worth considering as part of your compensation package. Getting even a 6-figure cashout after taking a 5-figure paycut for 10 years isn't necessarily even a break-even for you. You might have LOST money on that deal. As such, the equity is NOT there (and shouldn't be interpreted) as a cash-like form of compensation. It is not that. It is motivation for you to get the company to Facebook status. That's all it is. So, back to OP's question: why give so little? Because if the company gave you more, you would be tempted to build a 100m company, and that's just not gonna cut it. Instead, many companies would rather motivate a larger group of people to want it to be a Facebook-level enterprise someday.