What is the purpose and/or function of plastic engine covers?

What is the purpose and/or function of plastic engine covers?

Pretty
Reduce noise

Noise cancellation, Cooling, and becuase modern engines look like Medusa's head when you take the covers off.

press photos. why do you think everything with a screen is glossy when it leaves fingerprints everywhere?
noise reduction
air ducting

Why don't they just design better looking engines?

because physics dictates where parts go, not looks.

But the Italians can do it

that design only works with longitudinal high angle V configured engines

Working on a modern engine

So millennials never bother wrenching