My guess (and this is only a guess) is that this is the power of anecdote. Within certain communities, everyone knows someone who lost their job or had their business close due to direct competition with someone being paid under the table illegally. Any politician who claimed that it was a good thing would read as so clearly out of touch with lived experience that it's not worth the trouble to look past the soundbite.
It's the same sort of difficult argument as globalization and free trade. It hits you somewhere very easy to notice, so you feel like you're worse off even while you're sitting on your brand new couch watching whatever you want on demand on your 60" TV and eating your steak dinner. Making the link that all those other good things are a result of the same policy requires a small but not automatic intellectual leap that a lot of people clearly aren't prepared to make if they feel like the initial assertion doesn't pass the smell test.
It's the same sort of difficult argument as globalization and free trade. It hits you somewhere very easy to notice, so you feel like you're worse off even while you're sitting on your brand new couch watching whatever you want on demand on your 60" TV and eating your steak dinner. Making the link that all those other good things are a result of the same policy requires a small but not automatic intellectual leap that a lot of people clearly aren't prepared to make if they feel like the initial assertion doesn't pass the smell test.