Why can't I book a seat when I travel with a baby?

People with infants under 2 cannot pre-book their seats online.
Rows or seats are dedicated to families accompanied by infants and are only allocated at check-in so as not to separate families.
Regulations require a certain number of seats on board to be safe as they are equipped with a double oxygen mask (1 for the adult and 1 for the infant). 

These seats are therefore blocked at the time of booking and cannot be allocated to passengers without babies before check-in at the airport. They are first assigned in priority to adults travelling with an infant by our staff, then are made available to other passengers only if there are no more parents with infants who require this type of seat during the flight. 
That's why when you travel with an infant under 2 we block your choice of seat before departure, to make sure you will travel in a specific seat combining adult/infant safety.