What? Caseless ammunition is waaaaayyyyy more expensive than cased. Even allowing for tech advances reducing the cost to produce, cased ammunition is still 1) cheaper to produce, 2) easier to mass manufacture (i.e. cheaper) and 3) easier to reload (which makes it cheaper to maintain). When you are talking about multinational corporations, then the obvious advantage goes to the less expensive ammunition.
Sure, caseless is cleaner than cased ammunition in a weapon (with no open breach to eject the case, the interior of the weapon is exposed to fewer contaminants), but cleaning kits are an inexpensive option. Only spec ops units would be equipped with caseless ammunition, due to their specialized needs. Since you are blowing a bundle on spec ops training anyway, often the spec ops are given high end equipment to allow your expensive investment to carry out their missions without dying a lot (thus cutting into the bottom line for training replacements).
For generic grunts? The least expensive, mass-produced weapon/ammunition combination possible that will let them carry out their fuction. Which is usually taking ground or surrounding an objective and laying down a lot of firepower. Your grunts are going to die a lot, so why bother spending bunches of extra money on them.
