peripheral focus
Price. They can offer 24-70/4 in a set for an effective price of around $500-600 and still make money from it. That won’t be possible with the new lens.
All in all, if you can’t figure out why a camera company would do something, the answer is usually price. In terms of sales drivers, the three most important factors in a camera or lens are: price, price, and lastly, price.
That is true of the vast majority of consumer products.
