Why in the fuck does there have to be an entire goddamn wall dedicated only to toothpaste?
I can understand if maybe there would be more than just one, for stuff like people with sensitive teeth n shit like that, but there does not need to be like a hundred different tubes of teeth cleaning goo, all claiming to do something super duper special that all the others don't.
The reason this exists is because of marketing.
Line extensions create a "billboard" effect-- think of the 30-40 different kinds of oreos or flavored vodkas for example. They don't care how well the line extensions do, because now it creates a solid visual block of branding in a crowded and competitive grocery market.
The second reason line extensions exist is to engage consumers back to the core brand. Much how like well established brands continue to spend billions in ads (McDonald's, Nike, etc) these line extensions only serve as ad vehicles to remind you they exist. Why do we need to know about new "innovate" products at Taco Bell? Because now commercials have a new talking point.
And who knows, every once in a while, some "innovation" does ok. But really it's inconsequential if it does or not. It's just marketing, usually by big food and packaged goods brands, creating the illusion of choice. Usually, it's just a handful of big companies that create new brands or buy out other brands. Like Tom's of Maine is actually owned by Colgate, or Ben & Jerry's is actually owned by Unilever for example.
Some big companies even compete among themselves-- for example Diageo, the biggest liquor company in the world owns both Don Julio and Casamigos-- high end aspirational tequilas. But in many states they are distributed under different division houses to maximize sales.
The fear is if the same salesperson sold both, they'd have to pick one or the other to focus in any given market. But now with one distributor pushing Don Julio and another distributor house pushing Casamigos, you now have two sales reps dedicated to the brands respectively, instead of one who might muddle the two brands together.
I'm not saying it's good or rational, but that's why the 50 different types of toothpaste exist. Marketing is an extremely wasteful industry for environmental waste, people's time, money, and resources.