Not everyone is the same, so why do u have to have thrvsame plan for each person or why can't u transfer data from one to the other. I.e if u have two all rounder plans and I use all the 6gb data but to my wife only uses 2gb u should be able to transfer a % to me or visa versa. Otherwise the saving for the two R pointless unless u use equal amounts. We're currently on EE 5gb each (10gb to share) and they allow u to do it. my wife only uses 2gb and I transfer the rest. With bt u can't be flexible with plans or u lose the savings. Anyone else in same boat...?
Each network offers different plans to compete against each other, all offering some sort of USP. EE currently offer Apple music for example to its customers.
BT Mobile offers the family Sim, I get what what you are saying about users being different but for each sim you get the prices drops thats BT Mobiles USP, that and mose sim only deals are way cheaper than most networks. If all mobile providers offered the same plans and the same prices we wouldnt have a choice.
BT Mobile is still fairly new, and still evolving so who knows what they may offer in the future...