Does this TV cabinet need the screws or can it rest on the frame?
Depending on the material and the screws you may not need pilot holes; just a little force to get them started.
The shelf will provide additional lateral stability. Whether or not you need it is an engineering question. I would definitely want that added stability.
Sometime in the future, when you decide to slide the TV on the table top, e.g., for dusting or adjusting cables, you will be glad the screws are there. You or someone else will likely have forgotten the screws aren't there and when the top slides off enough to drop the TV you will rue the day you said no to the screws. (Not that I'm speaking from personal experience or anything.)