Lack Of Assault Rifles with Grenade Launcher Mount

So basically title, why does an Assault class, the only class with an access to underbarrel grenade launchers, breach launcher and UGL shotgun only has 4 rifles out of 8 with an access to the underbarrel mount? 
Not only this leads to much more limited selection of weapons with assault class proficiency, but also handicaps class ability to actually assault and retain mobility with devices designed specifically to break through the line of defense and breach entrenchments?

Of course there are apparently carbines with ability to stick grenade launcher mount on them, but they are not Assault Class signature weapons the class is proficient with, these are Engineer class weapons.
And Engineer doesnt have any gadget that can be strapped on a weapon using underbarrel mount, so what gives? 

Did M4A1, M277 and M417A2 suppose to be Assault Rifles in first place? Since M277 is an assault rifle in Battlefield 2042, I suppose thats what it is.

Can we get this fixed and get grenade launcher mount for the rest of ARs? Thank you