There has been a revolution in glass technology and lens manufacture and design over the past forty years. Just means lenses are not expensive and can be configured in any design easily enough.
Add that to cad design laser machining then manufacturing a scope isn't too difficult or costly.

Thing is there is a bit to getting the right combination of lenses, design, coatings, and all working together. Some scopes just are better designed, built, and just better in variable light conditions.

Air Rifle's put quite a lot of demand on a scope. 10 to 45m range makes it tricky and demands parallax and the more sensitive that is the higher the mag.
The more features the more to design right and the more to get wrong.
And then there is how robust to make it all, and how repeatable it can stay over time.

Basically, there is more to making a great scope as there is plenty to get wrong. Those manufacturers with the newest machinery tend to get more right, but only if they know what they are doing. Early Chinese scopes weren't great because they didn't really know what made a great scope. But with collaboration with brands that had more experience they have got a whole lot better. Now most reasonably priced scopes are pretty good.
As scopes have become cheaper to make then more of the costs has gone into the marketing in a crowded market. High end scopes still cost a bomb.

Manufacturers tend to make too many options, rather than make fewer, made better, that actually suit the few needs that are actually used in practice. I should think six scope variations might cover everything the market needs.