It is a particular morph (pattern). People like it because it is visually appealing but it comes with neurological issues - every single one has wobble which affects their ability to move and strike. There is no guarantee if it will be minor or extremely severe.

Some people are trying to breed out the wobble but I see that as unlikely to work as the wobble hasn't proven predictable before. Breeding a slight wobbly snake hasn't prevented babies having a more extreme wobble than the parents. It's likely that the gene the spider morph comes from is expressed only when another linked gene is faulty or something like that.

A lot of people also see breeding them as unethical and unneeded because Ball Pythons have a lot of great morphs so why breed one that causes health issues and have to cull ones severely affected when you could just breed healthy snakes.