racedo - you've completely understood how Ryanair can benefit from having a loyalty scheme and the inherent possible uses that comes from big data.
The problem is that plenty of passengers won't give that data until there is something in it for the customer as well. Additionally, loyalty schemes make passengers behave irrationally and prefer earning hard-to-use points or feeling affinity to a brand when they are probably better off just going for the cheapest vendor in the market.
Thus, why is Ryanair being reluctant to give some sort of reward for a customer sharing their data or otherwise offer some sort of tangible benefit that becomes worthwhile if flying Ryanair (rather than any other airline) on a regular basis ?
Companies can compete on cost alone, but trying to bamboozle people through marketing schemes makes it much easier to earn more profit.