There’s a mystery for me why people are using this kind of social media format.

This depends on your expectations. You can actually use Mastodon without any interaction, if you just want to read the latest updates from organisations of Thunderbird, Nextcloud, and read some poetry or stories via Writefreely blogs, and check out the uploaded photos from your friends on Pixelfed, and check out the latest videos of your favourite Peertube server, so that your Mastodon is a kind of RSS feed reader. Yes, with Mastodon you can follow users from all these different platforms. I think you can even follow Lemmy users ?

Besides that, after a full day of work, lying on the couch, scrolling though some belated Caturday pictures may be easier and more relaxing than reading long discussions on Lobsters ;)

I suggest to explore the options of Mastodon a bit more before deleting your account.