Mass transportation means you can profit from slavery or human rights abuses or whatever, while not seeing it because of the distance.

Slavery is more common than you think, and especially because there are conditions equal to any definition of slavery, which are just not labeled that. There still is plenty of such slavery almost all around the world.

Also, slavery is not the standard for exploitation. Subsistence wages alone may or may not be exploitative, but they don't constitute slavery. You need additional restrictions, for example on your movement, choice of work, human rights, etc