What is the difference between Amazon giving me, an imaginary Amazon employee, $100 in cash vs $100 in stock? Amazon is a publicly traded company, so any employee can choose to buy stock. Is the idea to force the employees to hold the stock without being allowed to sell it? If they can't sell it, what value do they get from it?

As an investment strategy, I never hold stock in a company I'm working for. That puts too many eggs in one basket. If the company fails for some reason, not only have I lost my job but I've also lost my retirement savings. I would personally oppose being compensated in company stock and would sell it ASAP if given the option.