There is a bit of a difference between someone who is denied entry at the border, and someone who is allowed entry, fully documented, given work permits, and have been in the country for several years.

Being denied entry at the border, isn't something that I would risk if I was planning a holiday or even an extended visit. That's just a good way to ruin everyone's plans and waste a bunch of money. I can totally understand why people wouldn't come here and risk that denial even when they have a visa in hand.