Tough skin reduces the number of animal species capable of stealing it’s hard-won cache of water, for one.
While it is true to some extent that evolution can be without purpose and mutations not beneficial, that tends to be for relatively minor traits. Say a plant species has 12 petals on it’s flower but closely related species have only 8. But major morphological features like the armored tuber, you better believe that it is adaptive. Organisms might can afford minor pointless traits, not so much major ones.
I think you make the mistake of thinking that the strange appearance itself is adaptive. Instead, it is just the result of the plant evolving a very thick bark to protect itself from herbivores. The plant doesn’t care what it looks like.
There are some mechanical/practical reasons the plant looks like that.
Given: the bulbous structure serves the purpose of storing food and water…
The plant looks to be adapted for doing that above ground (this may be an adaptation to rocky soils where an underground tuber cannot expand and grow much.
Growing above ground exposes this food store to attack by animals, and dehydration from exposure to sunlight.
The corky bark provides good protection against both of those threats, but is not a stretchy material, so in order for the tuber to be able to grow, the bark must be divided into plates or scales - actually, this is very similar to the bark of an oak tree - if you look at this stock image of oak bark: https://www.alamy.com/stock-photo-close-up-of-an-oak-trees-bark-38162480.html
The reason the segments here are narrower at the outward facing side than the base is that the plant is growing - so when the crests of the bark segments were new, they were big enough to span the surface of the plant; as the plant grew, they were pushed up by new growth underneath, which had to be slightly larger in order to still span the surface of the plant as it got bigger
Another weird (from our perspective) plant is the mountain buffalo. Its tuber isn’t armored, but it is huge. And one of my favorites that is like something from an alien planet in a SF movie is Welwitschiamirabilis, which only ever has two leaves, which grow continuously for sometimes well over 1,000 years. And everybody knows the giant flower of the parasitic rafflesia, but I like these more.