Can wire ramps alone cause bumblefoot?

I recently got a used DCN for my small army of boys and it came with some wire ramps. All cages I’ve had prior to this have had plastic ramps so I never had to think about this.

Wondering if anyone has any insight on if my boys risk getting bumblefoot if only the ramps are exposed wire? They do not spend a lot of time on the ramps, and I’ve put in more rope nets and other stuff as alternatives.

I have them covered right now with liners but was wondering if this is necessary?

Plus tax of some of my handsomes :)