Why weren't there much Rider shows in the 80s?

[cobabooy]

I understand that Ishinomori intended to end the franchise with Stronger until public demanded for more, which resulted in Skyrider. However, we only have 4 series (Skyrider, Super 1, BLACK & RX) and a TV Special ZX before dissapear from TV completely in the 90s. Was there any explanation why Toei didn't produce Rider series yearly like Sentai in the 80s?

 

[NeonZ]

Super-1 had a pretty big ratings drop from Skyrider, followed by a timeslot change. That probably killed the Rider series at that point. Regarding the later stop at Black RX, one of RX's main producers is quoted as saying that he didn't want to work on the franchise anymore after the Kamen Norida parody was allowed to exist and even blessed by Ishinomori.

Remember that Toei also had Metal Hero going strong at the time (and Metal Hero is completely owned by them, unlike Rider). So, dropping Rider likely wasn't hard back then. Without interest from the main producer, they just let it rest even though Black RX was fairly successful.