system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If we can store up to 128GB on a micro SD card, why are we still using big bulky hard drives in computers?

Why not just use SD cards for all storage purposes? 


Also, if we can compress files and make them way smaller than their original size (.zip), why don't we just store files that way all the time?
gpt
* they are more expensive
* they wear out more quickly
* we do, they are called solid state drives (SSDs)
* SD *cards* typically have slower read and write speeds (as pointed out by brunoa)

As for zip files, they are kind of like a toolbox.  When you aren't using them, everything is packed away neatly.  But while you are working on a project, you open them up and spread tools all over the place.  Only using zip files would be like only being able to have one tool out of your toolbox at a time.