This is a picture of the causeway jam coming into S'pore from Johor Bahru at 7:20am this rainy morning. It is estimated that 300,000 malaysians cross the border daily to work in S'pore.
Hassle of waking up earlier & immigration is worth it when considering the extra firepower from converting earned S$ back to RM$. Furthermore the costs of living in Malaysia is much lower than in S'pore. After a couple of years of work, one can own a decent freehold home with decent retirement $ in S'pore compared to their S'porean colleagues which are heavily laden with 30year housing lease loans & high costs of living in an increasingly crowded hectic environment.
When a person is paid in S$ & go back to their home country to spend with increased purchasing power, he/she tend to be obedient at work & not make waves. Why jeopardise the currency arbitrage they enjoy?(no offense to foreigners) When a corporation/institution is filled with these people, it just goes into a slow & lumbering mode compared to start-ups & fast growth small companies.
During weekends, S'poreans jam up on the causeway to head over to Johor for similar reasons-stretch their dollars further there instead of paying rental component in S'pore.