Help me understand the use of a rear sway bar

[Alex]

I do not really understnad the use of the rear say bar and here is why:
A high performance beetle is a heavily oversteering car. Adding a rear swaybar actually increases it. To have less of an oversteer you need to add a front sway bar to get more understeer. If you get an adjustable front swaybar you could dial it in.

So why use a rear sway bar?

Alex