Why?

Each is probably equally important:

Alignment. To better align personal incentives with the mission of the company.
Retention. To incentivize people to push the mission further for longer (stay longer at MUI, not too much, e.g. 10 years, but enough to differentiate from the competition) e.g. I have the opportunity to work on a new shiny project with a lot of potential, so why not jump ship?
Motivation. The team is what got us here. Improve the feeling of fair value distribution. e.g. If my work leads to x10 the revenues of the company. Why is my financial compensation not proportionally correlated to this outcome?
Hiring. To attract the best talent. e.g. Why should I accept the offer of MUI over Google?

Characteristics

1-year cliff, simplify the operations in case of mis-hires.
4-year vesting
Monthly vesting, not annual to avoid anniversary effects.
In this spirit, we apply the following function (exp(3x-3)) to determine the stock option package based on the FTE ratio.
Significantly more advantageous to full-time employees Non full-time employees, as we are in a winner-takes-it-all market.

How many Stock options are granted?

Principle

The idea of the number of shares distributed is that if during your tenure (from when you join to when you leave) the company grows by a factor Z, then you earn in the order of Z your annual salary, e.g. Z = 10.

Definitions

gross equity value, in dollars, that they will receive (based on our compensation bands).
common stock fair market value (“common FMV”), which becomes the “strike price” or “exercise price” that they have to pay to exercise their options.
preferred stock price, or the latest amount that investors paid for MUI preferred shares.