1. Mandatory I-9 verification means you will not be able to work at any large or non-shady company. No more highly paid tech jobs.
2. You can not re-enter and therefore you cannot leave, e.g. to see your parents in your home country, business trips or international vacations.
3. You cannot renew your drivers license past your visa expiration date. At best you can get a worse alternative (depends on state; AB60 in California) that lets you drive and not much more.
4. You would live in fear of ICE. After going through the legal immigration system, I cannot even imagine the stress of interacting with the illegal immigration system.
5. At that point your chance of naturalization is gone. Even everything else being equal, leaving and legally coming back on another H-1B would've been a _much_ more appealing option.
And I don't think any illegal immigrants would be laughing at the efforts of legal immigrants. I am shocked that you would write that. I am pretty sure nearly all illegal immigrants would love to follow a legal path if there was one that was achievable for them. After all, undocumented immigrants currently pay billions of dollars in state and federal taxes every year.