To illustrate @datakick's point even more, these are some of the scenarios that we were facing.
For some reason paypal requires states to specific countries depending on where the paypal account is located. So like me being in America, I might be able to have people order from japan fine. But a shop in Germany might require japanese states (prefectures) to be passed in the address. This makes things extremely complicated since there is no published list we could find. So the easiest thing to do was to remove the address from being sent. Its better to not get an address than to have transactions not work.
As for the line items, paypal is the only gateway I have seen that actually uses math on the line items.
Here is a scenario I was seeing happen. If you have a $10 product on sale for 33% off, the price is 6.666666~ So we would just round that to 6.67 and that would be the end of it. What happens if someone buys 3 of those products? What should the price be? Should the price be 20.00? Or 20.01? Paypal applies their own rounding, which is different than the merchant rounding. When that happens and the price if off, it gets kicked out on paypals side as an invalid transaction. There is not chance to actually pass the amount to paypal and adjust it when it comes back to the shop, its just a hard "This transaction cannot be processed" error when the user goes to the paypal site.
So those are the reasons we removed the data, since removing it there has not been one transaction related bug post / issue either.