The obvious answer is "Reasons".

@Strawberry Shortcake said:

The Avengers and Fantastic Four live act in public, they do not hide their real identities, so why would Spiderman be different?

Don't they, though, for the most part? I'm not a superhero nerd but the Marvel books seem to use the "secret identity" theme a lot to develop romantic stories and provide opportunities to create drama around the threat to their friends' and lovers' lives. In most cases, the "heroes" either use alter-egos to protect those that they care about or they are loners who don't have a long-term partner.

• Bruce Banner/ The Hulk. By and large he's a loner and tries to remain anonymous as he seeks a cure for his condition. When his identity is discovered, he usually tries to disappear again and assume another name. He knows that anyone near him when he "Hulks-out" is at risk
• Hawkeye. He has a private life that he protects from the public as he wants normalcy and doesn't want to risk the lives of his family.
• Black Widow. She doesn't have personal relationships, with perhaps the exception of Hawkeye. But that's a friendship and not a romance.
• Tony Stark. With the exception of Pepper Pots, a relationship that developed after he went public with his Iron Man identity, he's not known for having close personal relationships. He was already a widely known multi-billionaire with an immense security network, so he had the means to protect himself that most others in The Avengers lack
• Thor. Hell, he doesn't even live on Earth most of the time. And he doesn't have a private identity anyway.
• Captain America. The only woman he loved is dead and he doesn't seem to have any romantic entanglements to protect. Arguably, Steve Rogers isn't a secret identity.
• Falcon. Again, what secret identity?
• War Machine. Not really an Avenger that has a strong identity without the presence of Iron Man.
  

Idk. I always understood Peter Parker/Spider Man to be a loner because his enemies, when they found out his secret identity, would ALWAYS focus on attempting to kill his family members. The threat of harm to his family and friends is a central theme of the entire Spider-Man series. (IIRC his love interest, Mary Jane, was killed by Hobgoblin in one of the comic series once he discovered Spider-Man's secret identity.) There's been a pretty consistent theme in most comics that alter egos are used to either protect their loved ones or to allow them some measure of privacy so that they can live "normal" lives. You'd have to wonder how many modern celebrities would love to have an alter ego so that they could spend a little time out of the spotlight now and then.

No superhero should ever be exposing themselves in public...

@Strawberry Shortcake said:

The Avengers and Fantastic Four live act in public, they do not hide their real identities, so why would Spiderman be different?

What happened in the beginning of the film was unpleasant, but Peter could get used to that. In case of lawsuits, the Avengers could help him.

Hypothetically:

I am the Green Goblin. You are Spider-Man. I know your secret identity is Peter Parker. Because I know your identity, I learn that you have an aunt who lives in Queens and a girlfriend who attends your high school. I will then detonate an explosive device on the Staten Island ferry (or in the subway or in a high rise). While you are rescuing those people, I will kidnap Aunt May and MJ. Then I will send you one of their fingers each day until you agree to go to every bank in Manhattan and rob it for me.

Do you think that keeping your identity secret could be a good thing?

Does anyone know if the Spiderman series will ever come to Disney+?

Hypothetically:

I am the Green Goblin. You are Spider-Man. I know your secret identity is Peter Parker. Because I know your identity, I learn that you have an aunt who lives in Queens and a girlfriend who attends your high school. I will then detonate an explosive device on the Staten Island ferry (or in the subway or in a high rise). While you are rescuing those people, I will kidnap Aunt May and MJ. Then I will send you one of their fingers each day until you agree to go to every bank in Manhattan and rob it for me.

Do you think that keeping your identity secret could be a good thing?

Sure, but why then the Avengers do not keep their identities secret too? Some of them (like Clinton) have families and friends they care about. By your logic, they should too, but they don't.

I like it

@Strawberry Shortcake said:

Sure, but why then the Avengers do not keep their identities secret too? Some of them (like Clinton) have families and friends they care about. By your logic, they should too, but they don't.

Cause hardly anyone knows about Clint's family. He purposely kept them secret with S.H.I.E.L.D's help. The most anyone outside of the Avengers have learned about them were their names, which Kingpin was somehow able to obtain.