I don't know. I think it really started back when Disney had the rights to make Power Rangers shows. Instead of adapting Shinkenger, they made a "reversioned" version of the first (U.S.) season. Then Saban Brands came along and got those rights. I think it has less to do with (IMO) silly reasons like that*, and mainly has to do with Nickelodeon's inconsistent rule that every season must have at least 20 episodes. That's why they keep dividing adaptations into two separate seasons. Maybe things will change with Dino Fury? We can all only wait and see what happens...
*There are unconfirmed rumors and speculation that ToQger was skipped because they felt viewers wouldn't think trains were all that great, but I really doubt it. Also, Theagames10, do you have a reliable source that says those were the actual reasons why they skipped Kyuranger, because I sincerely doubt that really is why they skipped it.