Unlike BT lines, where the end user can choose whether to do PPPoE or PPPoA on the line, BE lines can only do one or the other and currently all lines are ordered for PPPoA unless you know to ask for the order to be provided as PPPoE.
Doubtless that is fine for most people, but if you are mixing the lines with BT FTTC lines (which are always PPPoE) then it can be easier to have all lines working the same way so that it is easier to bond them together.