Structure, guidance, accountability, connections. At least theoretically.

It's wonderful that so much material is free, but it's an overwhelming amount of information for the uninitiated. Some people can self-motivate and self-teach starting from zero. Some cannot. Some would just prefer a formal curriculum and instructor. Nothing wrong with that.

And the best bootcamps have a direct relationship into companies for internships and junior dev positions.

Unfortunately as bootcamp hype has exploded, many bootcamps do not offer these things and are of dubious value.