Some are also designed to be impossible to satisfy so that they can bring non-local talent to satisfy Labour Market tests. Not sure if it is in this case, but there have been plenty of such cases in the past.
Note that I'm not just talking about US. Most countries in Europe have the Labour Market tests requirement before a foreigner can be sponsored for the position.
Whoever issues the letter assumes liability for what they attest to.
It's not like people don't lie on these forms and get falsified evidence. There are cases of people getting caught, and people who did attest to the falsified evidence have had their green cards revoked and deported.
Kinda like IRS I guess.