Assault rifle and carbine class missing underslung mount?

Hey there EA community,  I thought id start of by saying I’m a frequent player on battlefield 6 and have been playing battlefield since bad company  

just curious as to why you can’t you put the “underslung  mount on guns like the ak4d or the nvo-228e, kord 6p67, the qbz-192 or any other carbine that seems to be missing that attachment? Are there not examples of these weapons in previous games or in real life that have those attachments?