Why did the TMNT kick the butt of Shredder so often in the 1987 cartoon?

[Original TMNT Cartoon Fan]

Why did the TMNT kick the butt of Shredder so often in the 1987 cartoon?

Not until season 9 Dregg appeared, at least giving some new stories. Did kids mostly care for the Shredder episodes? Season 4-5 had at least some solo adventures set in rural USA with street punk gangs, gangsters, other aliens than Krang but I don't know if kids liked them.

*In Mirage they just finish him off in the first story, then fight Foot Clan, street punk gangs, gangsters, aliens from other planets like Triceratons who attack the Earth and whatever.
*Archie had a big number of bad guys and girls (but I though Null could be a human). For a while it was like they tried to write him out of the continuing stories before returning in the Future Shark Trilogy with Armaggon and Verminator X.
*In the movies, the TMNT defeat Shredder, but he survives and returns in the second. But then the third and fourth had other enemies.
*Next Mutations had Dragon Lord, Shredder sometimes.
*The 2003 cartoon followed Mirage-Image, so they had more no Shredder stories.

If it wasn't for the 1987 cartoon (and the UK Hero Turtles comics where he also appeared very often), Shredder wouldn't probably be like a something you directly think of when thinking of TMNT.