Budget Travel - Ryan air - passport check for non-eu pax

What is the purpose of Ryanair checking non-eu pax passports and boarding passes before security? Is it to check the passport against the boarding pass? Is it to check that the persons nationality enables them to travel to the onward destination? Or is it to check the visa status of the country they are departing from?

Mst of Ryanair's flights are intra-Europe between countries whose citizens have, under EU law, a right of entry to the other country.

They check passports from non-EU countries as they don't have that right and Ryanair doesn't want to find out they will be heavily fined if anyone is refused entry