Group Assignments vs Individual Assignments

In schools there are two kinds of assignments, group or individual.

Yes, i admit, some assignments are hard to be done alone by ourselves.

BUT, why does even a really easy assignment need to be done by groups?

This is what i always thinking of, then, sometimes i find it's better to do assignments alone than on groups. Why alone?

the first, it's hard to arrange a group work, one can attend, others can't, etc. when we're on individual, we can do the assignment anytime.

second, it's hard to find a group, sometimes i'd prefer the group to be chosen by the teachers than by ourselves. *yes,i'm the one who always left behind*

third, when people in group attend the group work just to play and mess around.

Those are based on personal experience, so then, i really really prefer to do anything individually. It's better to do those things alone. *Oh dear, i think i'm a little bit anti-social*