When travelling by train through several countries, for example, from Norway to Spain, travellers typically have to buy multiple separate tickets. Perhaps Oslo - Malmö, Malmö – Hamburg, Hamburg – Paris, Paris – Madrid might work. If using a service such as thetrainline, booking might be made easier, but one still gets multiple tickets. This is fine when everything goes well, but has consequences for passenger rights in case of missed connections due to delays or cancellations.
Do through tickets between arbitrary pairs of cities or stations such as Oslo - Madrid or Paris - Bucharest theoretically exist? They're not for sale on websites, but are there any other channels through which they could be sold, or do they simply not exist at all? I've used dedicated travel agents such as the Treinreiswinkel in the past, but was still issued seperate tickets. Of course, they do exist and are bookable online for some connections (Amsterdam - Barcelona, Hamburg - Milano), but I mean for arbitrary city pairs (like they exist for flights between almost all major airports, I believe). The question here is not whether they can be booked online (generally not), but if they theoretically exist at all (even if very difficult to buy in practice).
I am aware demand for this service is very small. Maybe 60 years ago, one could turn up at the station in Oslo and buy a through-ticket to Madrid? If it was possible in the past, the question would be: have those tickets ceased to exist, or just made (nearly?) impossible to buy?
(I seem to recall Interrail/EUrail + reservations may count as a single through ticket, but in this case the costs of replacing missed connections are relatively small compared to regular tickets, so I'm interested in the regular case.)