Why No Goosenecks?

only reason I switched to a 5er hitch is because my 2012 Chevy's bed is a lot deeper than my 03 was and hitching by myself was a pain.

Not sure but I don't think you can use a slider hitch with a GN. Not that everyone uses a slider but enough do that you would have to have different king pin setups. What do you order as a dealership?

I agree with what been said about structural problems with a GN. Not all 5'ers are allowed to have a GN adapter. That's saying they didn't build enough strength into their design for it.

It is ez to build a stout GN trailer when the main frame rails converge at the hitch point AND you are not trying to achieve 6 ft height above them. More of a challenge when the frame rails instead spread to 96 or 102 inch spacing and cross members are required to secure a hitch point.

I would also say that it would be one ugly trailer sitting at the campground. ;)

5er frames are simply not designed with the strength and structural integrity that gooseneck trailers are. Yes, less expensive (cheaper).
But as stated there are many who install gooseneck adapters to their 5ers and pull them with no problem. However some manufacturers will void the warranty if you do.
As far as the hitch, you can get 5th wheel hitches now that can be removed leaving the bed flat.

X2 to both posts.

Our equipment trailers are goosenecks, but two members of the family/camping crowd have recreational fivers.

Consensus here seems to be that the recreational fifth wheel hitch differs from the gooseneck mainly for the same reason that trailer makers make most such design choices: It's cheaper.

Just a guess on my part but I think the 5th wheel hitch puts less strain on the trailer hitch point. This would allow the manufacturers to put together a lighter, some would say poorly, designed trailer.

OTOH I know some people that have used a gooseneck adapter to pull a 5th wheel trailer and have had no issues. My BIL pulled his with an adapter and pulled a pretty good sized boat behind the 5th wheel and has had no problems. IMO the leverage created by the adapter seems like it could definitely create problems if the hitch area of the 5th wheel is marginal.