Aer Ryan, when did you last travel from Beauvais to Paris??
Air travel is about speed and functionality. Getting into Paris from the north is a pain and Beauvais is one of Ryanair's least functional in so far as it may not be the furthest point of landing from the supposed destination city but it is one of the longest journey times.
In the days of Skyways Coach Air services from Kent airports customers bought a London to Paris ticket knowing that the trip did what it said on the tin - coach, short flight, coach all included - and many wanted to avoid the sea crossing.
Ryanair advertise a flight from Shannon to Paris. Using Beauvais means the coach journey to/from Paris is always longer than the flight and the bus ticket isn't included.
The journey on the M7 from the Limerick area to Dublin is always going to be quicker than from Beauvais to Paris and Orly to Les Invalides or any other central Paris destination offers various options not available from Beauvais.
Travel choices may include loyalty to a local airport but that will be well down the list compared to overall journey time, cost and choice of service