[jacquesm]

It's usually not the immigrants not paying taxes, it is their employers not paying taxes.

Under the table work is not because they don't want to pay taxes, they'd be happy to. It is because they get paid by employers that prefer to hire cheap immigrants rather than to pay wage taxes and other withholdings.

One mans freeloading is anothers profiteering.

They are also quite limited in what government provided benefits they can partake in. Mostly the stuff that is already there for everybody else (infrastructure) as soon as they need more than that they are usually discovered and deported. Cheap labour is only good as long as it is cheap.