Vista - Why can’t files contain ? / \ : < >

They accept periods and not these things? This is sparta madness.

Filenames cannot contain characters that are interpretted by the OS as special or delimiting. The full list of invalid characters is \/:*?"<>| and, although not specifically mentioned, I would include . as well as that serves to separate the filename itself from the 3 character file extension.

\ File System. Used to separate folders in the path.
/ Internet. Used to separate folders in the path. Must be // immediately after the : delimiter.
: Used to delimit the source (drive letter or internet protocol) from the rest of the path.
* Multiple character wildcard. Useful for searching and command line functions.
? Single character wildcard. Useful for searching and command line functions.
" Used in command line functions where a required filename and/or path contains one or more space characters.
<> File redirection characters used in command line functions.
| Used in command line functions.

It's more of common knowledge than anything else