Some reasons:

1. Not every foreign student can afford a "paradise" on a Caribbean island

2. Not every foreign student has fast, stable internet and reliable electricity for online classes

3. Most of the world doesn't enjoy the free passport access US citizens have to the rest of the world.

The US will suffer if its international students can't get an education here without being told by the government to pack up and head for their favorite Caribbean island because we don't value their desire to contribute to our society.

Leaving aside that you actually have to be able to get to and stay on that island, lots of students definitely need the structure of an on-campus life to keep them moving in the right direction. I absolutely did.

Many international students actually come from those paradise climes. It's not a big draw for them.