You use your private key to verify ownership. In the digital world, this is the closet you can get to having the "original thing". You can disagree with this, but it doesnt matter because obviously the NFT market believes in this.
Some NFTs just sit there, the same way an original piece of art will just hang on a wall. However, some NFTs can have 'utility'. For example, owning one can qualify you to buy a piece that is exclusive to collectors of a particular artist. The artist can also verify holders and send out physical products. Some artists are using profits to re-invest in larger scale NFT projects as well, like virtual worlds and games.
Twitter followers are between $5-30 per thousand, and Discord server members look to be around $70-80 per thousand. People pulling crypto scams will frequently fake popularity, back in the ICO days it was standard to have a telegram channel filled with 20-30 thousand bots.