Why does Ryanair check non-EU passengers' visas on intra-Schengen and domestic flights?

Ryanair requires that all non-EU citizens report to the check-in counter to verify their immigration status, even on intra-Schengen and domestic flights. According to Ryanair's official website the rationale is that:
Non EU/EEA passengers must do this in order to ensure compliance with immigration authorities. We reserve the right to refuse travel, if there is a failure to comply with this requirement.
However most other airlines don't care about visas or residency permits on intra-Schengen flights and sometimes even let you fly without showing ID.
So the question is: why does Ryanair conduct those checks?
Note that the linked question is about how to fly as a non-EU passenger, not why Ryanair conducts the visa checks.
EDIT FROM 2017: Apparently Ryanair realized how dumb their policies were and they no longer require you to go through visa checks on intra-Schengen flights
Best Answer
I was flown domestic flight with Ryanair in Athens in July 2017 as non-EU citizen. The guy on Ryanair check in desk has told me that the visa check is not required for domestic flights. This means that Ryanair has changed their policy, or this is just less strict policy in single airport.
Update: please note that this flight was Greece to Greece. Intra-Schengen flights may have other policies.
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Why does Ryanair do visa check?
Non-EU/EEA passengers must do this in order to ensure compliance with immigration authorities. We reserve the right to refuse travel, if there is a failure to comply with this requirement. If you have been denied boarding and require clarification please return to the visa check desk at the airport.Does Ryanair check passport?
Ryanair is one of the most popular airlines offering routes across Europe for less. They insist that you must have a valid passport to board any of Ryanair's flights ahead of travel.Do airlines check visas?
Carriers will check that a third-country national travelling with a short-stay, single or double entry visa or travel authorisation has not already used the number of entries permitted with their visa.Who checks visa at airport?
The officer at primary inspection will verify your identity and check your name against various computer databases. The officers are on the lookout for people who might be a security risk or who are using a tourist or other nonimmigrant visa to gain entry to the United States for illegal purposes or a permanent stay.RyanAir check in for boarding pass (ENGLISH SUBTITLE)
Sources: Stack Exchange - This article follows the attribution requirements of Stack Exchange and is licensed under CC BY-SA 3.0.
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