Actually, they won't sue until they are arrested and about to be deported and have nothing to lose
Oh by the way, 9 illegals suing makes national headlines, which means it almost never happens. Probably 9,000 citizens sue their employers on a daily basis. Here is the news item headline.
Nine illegal immigrants who worked as janitors at Wal-Mart until they were arrested during federal raids last month have sued the company, accusing it of discriminating against them