I don't think RyanAir have planned this thinking that most people go away hiking in the mountains!! There are VERY few places where you will not be able to get signal for 7 days
Nothing Ryanair do is by chance; they are much too sophisticated and efficient for that.
Seven days is
operationally a completely arbitrary window. It's not as if they're going to base the equipment selection on the number of checkers-in ( only have B738s and that one B737! ).
There's no reason it couldn't be 30 days, or 91 to put it the other side of a standard Visa waiver period. Except money-making; they will have very carefully scrutinised the average duration between booked sectors and subtracted one day.
Sit back, relax and enjoy your flight - and ultimately - your holiday!
Difficult to relax wondering if one is going to be stung for 45 Euros x2 in order to return home. That's 10 hours of UK minimum-wage salary just for the privilege of checking-in.