1. Risk - you throw an SLA on services and can point fingers when shit hits the fan

2. Circular agreements - you get them to sell your goods/services in the region of their home country

3. These count as "Services" on the P&L and provide massive tax advantages to the company because these aren't treated as labor costs.

This may be from an old context in my brain since I worked with some of those companies, so those reasons may have changed or impact may have with various regulations, etc.