Most comparison sites will show you these routes, for example Kiwi lets me search indirect flights from where I am in a remote part of Spain to where I live the other side of Europe. There's no direct routes, but it gives me the option of connecting in Barcelona, Stansted or Hahn, or cheaper options if I want more that one stop. It also lets me search a whole month to find the cheapest flights in a given time period, and will provide options with different low-cost airlines if that's cheaper.
However if you book direct through these sites you are going to get the lowest ticketing class. With Ryanair that means you can't take anything more than a small bag onboard (since November you need to pay for a 10kg cabin bag, you can't drop it at the gate for free), and if you are in a group you will not be sitting next to each other, so it may be best to book directly through the airline's site.
The simple reason why Ryanair don't let you book multi-leg flights directly is because they don't want to be responsible for you missing a connection. It's ironic though, as compared to national European airlines I find their punctuality a lot better.
There are several other reasons for not wanting to handle connections, including complexity of IT systems, negotiations with airports (bag transfer is more complicated), and general airline processes. I imagine they will end up doing it, Easyjet have started to act as feeders for global airlines - it's a clever idea
However if you book direct through these sites you are going to get the lowest ticketing class. With Ryanair that means you can't take anything more than a small bag onboard (since November you need to pay for a 10kg cabin bag, you can't drop it at the gate for free), and if you are in a group you will not be sitting next to each other, so it may be best to book directly through the airline's site.
The simple reason why Ryanair don't let you book multi-leg flights directly is because they don't want to be responsible for you missing a connection. It's ironic though, as compared to national European airlines I find their punctuality a lot better.