The reasoning for using a magic memory stick is similar to why you should use a pandora battery. I mean really, you need to use both of them together if you want to increase the functionality of your PSP, so they go hand in hand. In fact, the reasoning is basically exactly the same. The magic memory stick allows you to unlock / unbrick / open up your PSP to virtually unlimited possibilities including the use of homemade creations in the PSP hacking community, the use of all sorts of new crazy cool games, and so much more. It’s just a great way to go!
You might think this all sounds too good to be true, but it isn’t! Tens of thousands if not hundreds of thousands if not maybe even millions of people have already taken the plunge and freed their PSPs from the confines of the factory default firmware, and you can do the same! If you still aren’t convinced just read up on it some more, do some more searches, check out all the PSP forums dedicated to making PSPs be essentially all they can be, and then if you still aren’t feeling it, well, you’re just weird