Look it from their perspective, Glow have already got 3 seasons and folks have already watched them. New subs can watch these seasons too. One other season is not going to extend their customers.
A brand new collection provides to their catalog, brings new customers, followers of Amell and that different guys and so forth. Current customers would have a brand new collection to look at!!
There’s much less incentive for Netflix to transcend season 2-3 for any collection except it might probably generate sufficient buzz like stranger issues and promote by itself.