It's a speciality of the Tornado tables which are mostly used in the US. It was introduced as a cost saving measure, because four additional figures are cheaper than a curved playing surface.

The curved corners in a traditional table are of course necessary to avoid the ball being dead in the corners. With three players you don't need a curved corner and can still always get the ball.

Here is a video of the ITSF world cup, where you can see that there is just a single goalie on every side: https://m.youtube.com/watch?v=3vnrAIOWDwo&pp=ygUOaXRzZiB3b3J...

There is actually a quite interesting documentary out there which tells the rise and fall of foosball in the US which is tightly coupled with the company behind the Tornado tables if I remember correctly. I saw it on Youtube a while a ago, but could not find it now. Might have been "Foosballers" but I am nit sure.

Thanks for all the answers. Perhaps it’s a US/Europe thing.

At least the official table of the International Table Soccer Federation only has one goalie, and raised corners.

https://www.tablesoccer.org/tables/leonhart.php

Now I need to quickly climb out of this rabbit hole before I start to dig into the 41 page rule book. https://www.tablesoccer.org/rules/documents/Standard_Matchpl...

I've never seen a table with 3 players in the goalie position in my life.

The tables I've seen with one goalie have raised corners so that the ball doesn't get stuck there. You see it more on budget tables in my experience.

The single goalie w the corner ramps was a late 1970s into the 80s things. Those are now less common as some competive foosball uses the three man rear, but there is one or more exceptions. I did the researh for my coed fraternity reunion, very hard to find the classic ramp tables, as they were made of particle board and degrade. The one company w ramps uses a more gentle slope rather than an added steep corner ramp.