If they can charge 1-2% of the goods value, then it is worth it for them.
Do you think 1-2% is big?
1-2% is not very much to charge, especially considering that most goods that shipping companies ship have very low values. The cost of a shipping company facilitating an average transaction would be much greater then the revenue generated from an average transaction. This would mean the shipping company would be forced to operate at a loss for most transactions.
Another issue is that when a fee is charged for escrow people are much less likely to tip the escrow service and tips on "free" escrow service can generally add up to a lot more then 1 or 2 percent