Sunfish,
As someone who still uses Ryanair a fair bit, I would guess they probably rely pretty heavily on repeat business. Considering Ireland only has 4 million people living there and Ryanair still derives a significant percentage (was about 40% 3 years ago, now? don't know but at a guess I'd still say in the region of 20% to 25%) of it's revenue from it's Irish operation I would say a lot of Irish people do put up with the minimal to ****e service levels time and time again because of one thing: price.
Examples are numerous - I used to do Dublin to Edinburgh one or twice a month with Aer Lingus - absolute minimum cost £100IR (€128). Then Ryanair came along and total average cost, about £50IR. Now how Ryanair arrived at doing this route is well known amongst the flying fraternity and how Ryanair treats it's pax and staff is equally well known and debated. But as a passenger I put up with all that for a relatively painless short-hop flight. Would I do the same for long-haul? Not a chance in hell.