They're different application types - friends + family relationship reinforcement, social commenting (which itself varies across various dimensions, from highlighting usefulness to unapologetically mindless entertainment), social content sharing and distribution (interest group, not necessarily personal, not specifically for profit), social marketing (buy my stuff), and political influence/opinion management.

Meta and X have glommed them all together and made them unworkable with opaque algorithmic control, to the detriment of all of them.

And then you have all of them colonised by ad tech, which distorts their operation.