[Jach]

> why is garbage collection needed to begin with?

Computers don't have infinite memory. If they did, there would be no need for garbage collection. So if your program needs more memory than the system has, you either need to buy more memory, or figure out areas of the existing memory space that can be overwritten, or rewrite your program to use less memory. (Some embedded systems developers never use free() because they know their code is the only running code and know it probably won't use all the device's memory.) You can manually figure out and mark memory that can be overwritten by using free(), which can be error-prone if you accidentally mark a block of memory as available that shouldn't be. Or you can let the programming language runtime figure it out itself according to whatever algorithm (such as, simplistically, "this block of memory won't ever be accessed again in the running code, we can reuse its memory"). Garbage collection algorithms can be a lot more sophisticated and use memory-sharing and other things, but the point is to make memory usage efficient and not something the programmer necessarily needs to worry about.