Currency differences would be a big reason. Currencies can shift against each other and if the dollar weakens or strengthens against the Euro or Yen or whatever, it would mean their payroll costs would fluctuate unpredictably.
The good news is that some countries won't bother taxing you if you're working for a US company remotely - they're just happy to have expats spending in the local economy.
I work for an engineering company in Switzerland, and half my team are German citizens who (pre-covid) made a daily commute all while enjoying the lower cost of living in Germany.
* I know it is not that, but it feels like that. Also thankfully not tied to the officially reported inflation rate in Turkey
For every Swiss Franc that strengthened 15% against the dollar in 10 years there's an Argentine Peso that because 45 times weaker in that time period.