It is true that many businesses engage in this illegal labor, but that doesn't mean we should keep it going. There was a time when most of these jobs were being done by citizens. Illegal labor eventually caused wage depression for these jobs, so citizens stopped working them. However, if you cut off the supply of illegal labor, then these businesses have to pay more to hire citizens. Some will undoubtedly fail as a result, but that's their fault for engaging in illegal labor to begin with.
To be clear, I have no problem with these businesses hiring immigrants legally, but typically, that would mean they would have to pay them more than they pay these illegals.