Why do the champs fight so sparingly now?

[KidDinamita]

They are making huge amounts of money as well, not feasible to fight more then that.

And also milking fights, until they either dont fight at all or fight when they are 70years old.

[Roadblock]

You can fight every 12 weeks , if the opponents are easy beats, when you get to the very top you can fight the very best guys maybe twice a year, level of competition is what governs how active you are.

[Curtis Harper]

Not every guy deserves a title shot.

There are multiple champs
5 ''legit'' contenders/gatekeepers
Dozens of journeymen.

The math doesn't support champs fighting top guys 4x a year.