Perhaps, but I value diversification of my investments. Investing my sweat and my equity into the same company is not diversifying. It'd also be easy for me to overestimate just how much they've derisked, underestimate the fine print, golden handcuffs, and generally fuck myself over.
Rounding to $0 is a useful and "safe" oversimplification. If they turn out to actually have value - hey, sweet, an unexpected bonus.
Absolutely. It's never an accurate assessment, but when the vast majority of people are in no position to even ballpark estimate the value of their equity package, rounding down to $0 prevents a lot of heartache.
I could see this being a valid argument if there were systemic risk to the industry that could have a simultaneous effect on your equity and salary compensation. e.g. if you're a truck driver and get equity in your company, then automated trucks could be disastrous and you'd want to diversify away from the equity.
Put another way, you're right that the equity is the only way that you are exposed to the company's success, but there are catastrophic ways you can be exposed to its failure.
Bad assumption. I've known people who lost a large chunk of their retirement funds in the dot-com bubble, despite "diversifying" within it. More recently, there was the housing bubble. Both of these had implications for the job market - and salaries - at the same time.
Some people would argue we're in the middle of a tech, games, or VC bubble - and while they might be wrong, diversification is what you do to mitigate the risk in case they're right.