First, a loft isnt essential. Piggies need a large single level space and as ground roaming animals, any upper levels are bonuses spaces only.
The ramp itself takes up space from the ground level. Wouldnt be so much of an issue in a cage of the size of yours, but for some it is.
You are right, lofts aren't big and the ramp can cause problems - but it is very piggy dependent. For some boars a ramp would cause a problem - it might mean one takes it as their own and refuses the let the other use it, issues with one trying to go up and one come down etc, for others they will use them without issue.
Personally, when I had a loft area in my boys cage, they went up there sporadically for a few days, the novelty wore off and they never set foot up there again. It was taken down and basically was a waste of time and money! They have such a large floor space that I dont think they ever felt the need to 'get away' by using a loft.