adding slide out topper

just bought an Open Range that came without slide toppers. I traded in a North Shore that had the toppers. In doing so, I noticed that most of the new fivers on the lot did not have toppers.

Question: Is there a general movement away from these, or is the manufacturer just trying to save a buck?

As a relative newbie, I'm curious what the general consensus is on the presence/absence of toppers. It's nice not to have to clean off slide before decamping, but hosing them off wasn't that big of a deal.

What's a ballpark cost to add?

Thanks.