So...watch culture in a country is something of a reflection of the society, so maybe the reason the OP doesn't see as many affordable mechanical choices (the "gap") is due to the attitude prevalent within the OP's country. The question is a reflection of what he sees in his own environment.
Sometimes these things are self-fulfilling prophecies. For example, perhaps the retail chains decided (whenever) that there was no market demand for non-luxury brand mechanical watches, and so declined to stock them. As a result, the companies which make the watches don't bother advertising in that market, and thus the consumers aren't aware of the brands, consequently they don't ask the retailers to carry them, which in turn reinforces the retailers' perception that no one in that market wants an affordable mechanical.
If that's the case, and I'm assuming it is, based on the OP's question and Mort's explanation, I do find that interesting from a business perspective, and I do agree it does present an opportunity, maybe. In order to justify the investment needed to raise consumer awareness and create demand, a brand would need to be certain of the return on that investment. Maybe the reason affordable mechanicals haven't been widely introduced to that market is because there really isn't enough of a market to credibly expect a high enough return on the investment needed.