If they work so they can afford school, rent, food, and other things. If they attend classes it is to get course work out of the way. Summer sessions are usually shorter and it means units that are finished making way for courses in the fall.
No, it's not really needed for university students to do so
No, it's not mandatory for university students to have a summer job.
Not wrong, but most University students need to earn money over the summer.
No, some do volunteer work, some take summer classes to finish their degree, and some of them stay home with their parents.
no
no
No
Yes
No
no
No
Lots of them