The attendance was horrible, but there are a list of things that can play into that and for each person and family it is different.
1) Royals the past 30 years, fans are worried we will fall on our face once again.
2) Weeknight and now also a school night
3) Heat
4) Location (nothing in the area but the stadium, nowhere to have post victory shenanigans)
5) Ticket/Parking Prices
I think location is a huge factor. Attendance average this year I think has been up, but I personally would be more motivated to go to a game if it was downtown (especially during the weeknights). The location now is horrible to say the least.