Is it common in any other first world countries besides the US to work while attending university? I have an old family friend in Japan (born and raised). We were recently talking about academics as he is in his 2nd year of Uni and I have 1 B.S and soon to have another with the goal of moving on to a Masters this fall. 

While talking he asked if I "Work or study" as he knew I completed my first degree but was unaware I started my second. When I mentioned that I both go to Uni and work a corporate job in my industry he was, no joke, speechless. 

He couldn't believe someone could both attend a Uni and work at the same time without failing classes. He told me that people only work part time jobs very sparingly during school semesters and then work more during the summer but can't even begin to believe working in a corporate job while still studying. 

I don't know too many people that attend my Uni and don't either have 2 part-time jobs or a full time jobs (except for those with free rides or very generous parents). 

Many people I know from other countries (I try to culture myself) ask me the same question "Do you work or study?" and they get very confused when I tell them "both" and explain my situation. 

Is this only common in the US? I've talked to people from Singapore, Japan, Canada, Greece, and the UK and they all can't believe working and going to Uni at the same time.
In Germany, at least one survey reports that 47 percent of students work during the semester, and 63 percent work during the holidays between semester.

Most of these students earn less than 500 Euros a month, but 6 percent earn more than 1000€ after taxes. Over 60 percent that have jobs have one to finance their studies/living expenses. For 7 percent of students, their job is their only source of income. 

According to the Sozialerhebung 2012 (a large survey by a federal agency)  figure 9.10, 13 percent of students studying towards their first degree  worked more than 20 hours a week on average in 2012. Whether that's "common" is a matter of interpretation. 

The part on financing reports a median income of 300€ from working, with 63 percent of students doing some kind of work. Figure 6.5 shows that 2 percent of students only finance through studies through work, with an average income of 960 Euro, and 13 percent mainly finance their life through working, with an average income of 660 Euros. 

(All sources in German)