They provide several benefits…1)they do offer some aero advantage, 2)they do function to protect the neck area, and 3)they do help with neck fatigue when you are in a racing crouch.
Most of them are removable via a zipper in the top(if the hump itself is permanently sewn on, there is an access zipper that allows for the foam to be removed), so if any of you know someone who has one, you could borrow it and do some trial and error stuff.
I’ve got one on my riding jacket I used on the street, but I nevr felt it was worth it because you’re not in a racing position on the street typically. I never had one on any of my race gear.