The saying goes if you’re not the customer, you’re the product. Now, you’re both. Every big social media app is testing subscriptions. It's a business model that comes with a perverse incentive. Just like airlines, if you make life worse, more people will pay.
I think you’re misreading it. In the same way as there are people that need to ride on planes (for example for their job, or to move to where they have a job, etc), there are people that need to use social media.
For example, if you own an online store you really need to have a social media presence. Same if you are an artist, and live off of commissions. I’m sure there are plenty more examples.
Also, Facebook groups are now how most extracurriculars are handled in schools, so if you have kids and you want to be involved in their activities you don’t have much of an option.