Why is like 90% of all sporting optics made in China? Cheap cost with reasonable quality for the masses.
As to why Vortex chose this route, only they can answer that. I can tell you that I have shared the complaints about the spotters with them, and recently returned all the Impact spotters I had after I spent some time with them. To their credit, they take it in stride. A great bunch of folks.
"See Better, Shoot Better"