* Storage: The PSP uses the memory stick to store game data, system files, and save files. Without one, there's no place for the console to store anything.
* Operating System: The PSP's operating system and software are also stored on the memory stick. Without it, the console won't be able to boot up.
Alternatives:
* PSP Go: The PSP Go model had built-in storage and didn't require a memory stick. However, these are no longer readily available.
* SD2VITA: For the PS Vita, there's an adapter called SD2VITA that lets you use an SD card instead of the official memory cards. However, this won't work on the original PSP.
* Custom Firmware: Some custom firmware options for the PSP allow users to access internal storage, but this process is technically complex and often involves voiding your warranty.
Conclusion:
The only reliable way to play games on a PSP is to use a memory stick. There are no official workarounds that don't involve the use of a memory stick.