@bride2bein10,
The designer placed it on the suit for practical rather then aesthetic reasons. You probably should use it, especially because
it's not a a great fitting jacket.
It's most likely a redundancy feature so that when you flailing around in a particularly turbulent area of water, the life jacket won't flip off over your head.
If you drown wearing the life jacket and the manufacturing company finds out you altered its safety design, don't expect your surviving relatives to make a successful lawsuit against the manufacturer to compensate for your potential Darwin Award winning mistake.