Providing a guarantee of a connection between 2 flights is a service for which BA are legally entitled to charge an additional fee at the time of booking provided it's all transparent before customer makes a booking. Whether they choose to make a charge or you think that's a good idea is a separate question.
BA are possibly preparing the ground against the likes of Ryanair providing official connections within Europe. You can be certain Ryanair will consider charging an extra fee to avoid pax having to self-connect; BA will want the option to do so as well. You are likely to find that 2 tickets are cheaper than 1 combined ticket primarily in the cheapest fare classes on routes where BA compete against LCCs on the individual sectors but the route involving the connection may well not have LCC competition. BA possibly want to charge a premium where they provide a connection guarantee without LCC competitors. Those flying in business class are less likely to see 2 separate tickets being cheaper overall than 1 combined ticket
Ultimately this is about BA short haul trying to focus their cheapest fares only where they absolutely have to compete against LCCs and not leaving money on the table by giving customers a possibility to essentially get the LCC-equivalent price where LCC competition doesn't exist
Last edited by davidjohnson6; 24th Apr 2017 at 11:11.