iPad screens are robust, but the anti-reflection treatment and oleophobic coating can be easily damaged by tiny grit/dust particles that are unavoidable in many environments. The oleophobic coating is a chemical sacrificial layer that will wear-out over time.
A Screen Protector provides an additional defensive barrier - protecting both the original screen finish and the oleophobic coating. The downside is, perhaps, an increase in screen reflectivity and a slight reduction in contrast.
Some users comment that a glass screen protector makes the screen slippery when using the Apple Pencil - for which the alternative is a matt/textured film screen protector - but these have two principal disadvantages.
1) The textured film reduces clarity and contrast
2) Accelerated wear of the Pencil tip, necessitating frequent tip replacement.
Your iPad screen is an expensive component of your iPad; unlike your screen, a screen protector is a sacrificial component that is easy and relatively cheap to replace.
Some contributors here will suggest that a screen protector is unnecessary - whilst others may be more cautious, favouring the additional protection afforded by a screen protector. It’s entirely your choice.
Zagg are amongst the better manufacturers of both tempered glass screen protectors and plastic laminates - with good reputation.
