>>1687861>you have to go through about half a dozen different separate websitesNot necessarily, but I can understand why you'd think that. It's like booking a hotel: whether you book direct with the hotel or go through a third-party like Expedia or whoever, you'll still end up with a room booking. Ultimately, whether you use Trainline or Trainpal or whatever, you'll get the same ticket whichever website you use. The reasoning behind signing up for accounts is because electronic tickets are a thing - buy a ticket using Trainline, log into the app on your phone, the ticket's there waiting to be used; scan the barcode during the 'tickets please' check and at the station's fare gates.
That said, you can buy tickets directly from train operators and perhaps save a little money - the downside being that these will usually have a (only valid on OPERATOR services) proviso, rather than a simple 'get me from A to B via the most reasonable route' thing. So if there's a delay or cancellation, it can be a headache finding the 'correct' train you're permitted to travel on.