"it's a global market and gm is concentrating on such a narrow market"
You may not like them, but believe me these trucks are their bread and butter and they are NOT after a narrow market. In many ways, it's more challenging to redesign a successful vehicle than one that isn't selling at all. Chrysler properly gets lots of credit for their bold 1994 truck redesign, but at the time their sales were lousy and they really had nothing to lose if it didn't work. As the market leaders, GM and Ford both have to be careful that they continue to change and improve their trucks without alienating their base audiences. Not always easy to do!