When you consider that the difference between successive sizes of dilators is 1/8"
that means that it's only 1/16" bigger in all directions.
If you dilated with something a bit squishy it would easily squeeze down 1/16" in the tight spots.
You don't want that, you want the tight spots to be stretched.
One of the tightest spots is the PC muscle, it's very strong.
You need something pretty hard to stretch that.
It's all not particularly comfortable, but also not particularly uncomfortable.