Because they need something to make them as cost effective as grens. also when you compare them to the 2 other cc troops you realise that other ones are better. assault grens are much cheaper have more durability and have sprint. shocks nearly have twice the durability of a pg squad not to mention smoke grenade to cover the advance.
the lack of smoke grenade , sprint and durability on top of that they are extremely expensive to reinforce makes the pg the weakest cc troops in the game. ther medium range firepower doesn't make up for that
They are NOT close combat troops any more!
I have had some great successes with them lately using them as the mid range unit. Wiping out 2 squads of Cons closing in on you - priceless.