Supply.
Most are removed when orders exceed capacity and delays are above given limits. Manufacturers will hit a point where losing Scheme orders is less of a problem than losing retail customers due to unrealistic manufacturing delays. I know the Elroq, Explorer and Capri were removed for order number related reasons. The Ioniq 6 has a new facelift coming out imminently which then stops current model orders so that everything can be setup for the new car.
I'm Autistic, if I say something you find offensive, please let me know, I can guarantee it was unintentional.
I'll try to give my honest opinion but am always open to learning.
Mark