In some countries, particularly in the developing world, full-time, live-in household help is more accessible than it is for most people at home. Wages are lower, and often times opportunities for other types of work are fewer.
At the same time, conditions in many of these countries make it difficult to operate a house without assistance. For example, “shopping” might mean visiting a number of markets at different times, bargaining aggressively and assembling the day's groceries over the course of several hours.
While such shopping adventures might be quite enjoyable at times, it may be impractical or even impossible to do all this while trying to also do the job your company sent you overseas to do in the first place.
In some places, household employees are part of a rental agreement, working at a particular home regardless of who is living there. In many places having a place to live attached to your own home is a significant part of the employee's compensation.