When I've arrived to Germany, the first thing I've need to do was to search for an appartment. What striked me, was hard for me to comprehend 'excentrity' of the landlords who required job contract (ehm, why is it important? better ask how much money I have on side...). It wasn't a problem for me because I've already got a job. But...
Consider typical expat situation. You want to settle in Germany. You come there to look for a job. You need an appartment... So how should you look for it to go over that 'job contract' requirement?
Is this 'additional requirement' a standard at all, or was it only a regional variation (Bavaria) or I simply had 'strange luck' when searching for appartment?