[Flamingoat]

It doesn't do that actually. It concatenates files. From the description on the man page:

    Concatenate FILE(s) to standard output.

    With no FILE, or when FILE is -, read standard input

https://man7.org/linux/man-pages/man1/cat.1.html

[atoav]

Yeah sure, that is what happens when you feed your cat multiple files.

Cat in 99% of the usage cases is used on one file

[Flamingoat]

No. What is stated by the manual is what cat does. What you said was simply incorrect.

It does have the effect of what you describe if one file is supplied and might be the most common use case. That doesn't make your description correct, at best it makes it incomplete.