Mastodon doesn't have that. Instead, you have to read a wall of instructions and explanations about all the reasons one doesn't simply sign up for Mastodon. Next, you're asked to make a life-changing decision about a concept you just learned about for the first time, assuming you bothered to read that entire wall of previously-mentioned text. That is all friction. It's almost like Mastodon doesn't want any users.
Not to mention that people are often (but not always) multifaceted. We like sports, but we also like gadgets. We like to participate but we also like to be entertained. We like music but we also like computer programming. We like video games, Broadway shows, going to the beach. We like both dogs and cats. But Mastodon wants us to choose one and only one thing. That's what's stopping the flow of more people to Mastodon. They need to fix this, and fast.