because if they had a full time employment their employer would have to give company benefits..see how this works?
nope.
MANY full time jobs dont offer "benefits" at all.
you see child, a long time ago, when this was still a cpitalist nation, if you wanted the best employees, you offered them more money, but in the late 30's a leftist marxist named Franklin Delano Roosevelt changed all that.
he made sweeping declarations which capped wages, forcing employers to find new ways around the wage caps, like offering free medical care , which eventually morphed in the the health insurance monster that ravages the kingdom today
another of the ways to dodge the evil twisted cripple's dictates was to offer "stock options" which has become the default choice in lieu of wages to doge taxation.
another of the monsters spawned by that degenerate gimp was the creation of the welfare state as we now know it. and while the leftists and marxists all feel good about the welfare state and how They (and by that i mean other people) are "Giving Back"
but then, as now, there are no mandatory "benefits" only ones which are expected by the brainless sheep who think that the way things are is the way they have always been.
thats right sweet pea, no mandatory benefits, not even if you work 40 hours a week.
The End.
and the reason many po-folks have 2 part time jobs is because thanks to Free Trade and Outsourcing (pioneered by BOTH THE LEFT AND THE RIGHT!) there are not enough real jobs out there.