I recently came back through Dublin airport and used e-Gates. On one of the signs, it said that one of the requirements besides being an EU/EEA passport holder is that the passenger must be over 18yrs old. I also saw this while arriving in Schiphol airport in the Netherlands?
Why is this? One of my friends who worked in the airport told me that it's a measure to prevent children being trafficked or 'stolen' by one parent if the other doesn't agree. In other words, they have to meet an immigration officer who would question them with greater detail about their travel.
Children over 14 can travel unaccompanied to various countries so I don't see what other reason there may be for this rule