How often early-stage startups build prototypes in low-cost countries?

I help startups build tech teams in Southeast Asia but JUST TO BE CLEAR I'm not here to sell anything. Since Product Hunt contains a lot of early-stage companies, I just like to understand why/why not founders choose to build their products in lower-cost countries, ie. Vietnam or the Philippines. I'm a big supporter of low-cost experimentation, especially when you are in the pre-product/market fit, in which your focus should be figuring out the look and feel of the app, figure out the critical flows in your site/app, like signing up and sharing, and what factors turn users into successful and active ones. Part of the process of achieving p/m fit is making repeated prototypes quickly. Nothing needs to scale, or work at the edge-cases, until it has product-market fit; and you might need to write two or twelve or twenty different iterations until you find one that works out that way. This is a very costly process, and many startups run out of cash before they even achieve product-market fit. So going through this process by building in low-cost countries seems to make sense on paper, but I'm not sure why there aren't more startups doing it (at least not enough founders chose this route from my perspective). I'm genuinely curious, so I post this question here. The obvious pro is: - Much lower cost The main con is: - Sometimes not easy to manage I always believe that brilliance is evenly distributed around the world, so I don't put talent quality as a factor. Your comments are much appreciated!