Social trends may play a role here. People seem to have been in love with "mini" for some time, particularly the types who might use the Instax cameras. I think there is also an atmosphere of style around this type of photography, and small seems to be ideal (Polaroid has been hugely popular for decades, and its photos were always fairly small....its an artistic and aesthetic appeal thing, I think.)
From an economic standpoint, if socially people prefer the "mini", that would increase demand for mini-compatible film. That boils down to simple supply and demand, which might be why a box of 20 minis is 20 euro, while a box of 20 wide is 22 euro. Also from an economic standpoint, it can be very difficult to tell why a film might be discontinued, or whether it may be discontinued forever. Fuji discontinued their Velvia 50 for a while, and popular demand for it made them bring it back only two years later, and its still a tremendously popular film for landscape photographers and pretty much anyone who wants rich, warm color from film. Similarly, Polaroid film was discontinued a few years ago, largely for economic reasons...a down economy, considerable increases in manufacturing expense, fewer buyers (even though its still quite popular), and general competitive struggles for Polaroid as a company in general. Its unknown whether official Polaroid film will ever be produced again (there has been some mention of a return of polaroid instant film cameras, but nothing seems concrete), however there are some dedicated and concerted efforts to produce it independently, to satisfy the desires of those who have and still do love the aesthetic and artistic appeal of Polaroid film.
So, one can never say what may happen with any particular type of film, and whether any significant changes may be permanent or not...it all depends on the social trends and economic viability of the times.