yes it is very much a cultural thing (see my longer comment) & often just makes economic sense. The argument that they are underpaid is relatively flawed. Servants in cities make much more than they would make if they stayed in their towns or villages an did nothing / worked on someone elses farm. If there is a minimum wage in all sectors with unorganized labour (construction, farming etc) - then yes - these people will be tempted to move there. But really - if you're making 10x cleaning a few houses a day - which is in no way risky / life threatening - why would you go work on a construction site or spend your days on a farm in 30+degrees C of heat?