I just replaced my spark plugs and I didn't fully connect one of the plug wires to the coil so when I drove it, the Engine symbol flashed. I stopped and rechecked my work, found the loose wires, reconnected and it's fine. However, it was a pain in the butt to take the engine cover off.

My question, other than aesthetics, does the engine cover serve any other purpose?

 

no.

they are just there for aesthetics.
and in fact, hold heat in.

these J-series engines are very prone to heat soak. by removing the plastic engine covers, you're letting heat escape and will have an easier time accessing your engine for maintenance

 

It may provide some sound deadening for engine noise?

 

purely aesthetic.