The final destination of divert doesn't solely end with EI, there are many other factors to take into consideration. Can ground handling be put into place at short notice, if the ground handler doesnt handle EI anywhere else it is hard to put in place details where the airline can be charged.
Other factors are can the airport accommodate the flight at that time, if there are numerous aircraft diverting, say an airline that is already based at the airport that airline will get preference to landing and precious ramp space for aircraft. Re-fuelling contracts is another factor - does the airline have contracts with the company that provides refuelling so that the aircraft can leave again, there are so many more factors to be considered in a diversion, obviously if the diversions is a mayday then u land at the next possible destination regardless of the consequences on the ground such as not having contracts in place as safety comes first.
I get that u have been annoyed and frustrated as its not nice for anyone to land at the wrong airport but there are other things to consider and its just not as black and white as you make it out.