Shinies are not fun getting or hunting anyways, there are no reward in getting one anyway as you will probably never get one when playing this game. But I agree that shiny pokemons should not be buyable from any shop in this game..
Conclusion: No fun hunting a shiny pokemon and no fun getting one since it is near impossible(counted 55.000 encounters and got no one). And if you finally get one there is a very HIGH possibilty it is just a common shiny or one you already own.