I don't think anybody has answered the first question in detail yet. But I don't think you can answer it without explaining why militaries train their soldiers the way they do (if you don't care just skip to my last paragraph). I, personally, feel that modern militaries train soldiers in forward hand techniques for at least three reasons.
First the blade is more useful in combat with modern body armor, you can cut through it (modern body armor disperses kinetic force rather than stopping it with a solid wall) and less of the body is protected. Historically you'd mostly have used the point to pierce vulnerable points on metal armor (which is much easier to do with reverse hand techniques), with basically no cutting targets.
Second is cutting (which is easiest in forward grips) gives you more control over the severity of injury (arguably) you can give an opponent. Hence (also arguably) more tactical use on the battlefield.
Third modern tactical webbing places combat knives on the chest so deploying it in forward grip is fastest and easiest.
This all circles around to why militaries don't issue daggers. They are not necessary on a modern battlefield to pierce armor. They are less useful in a utility/survival role than shorter single edge weapons. Good daggers are hard to mass produce. They also should not be made of stainless steel, which creates (possibly) maintenence and reliability problems with them.
