From Electronic Life:
Most users end up wanting more Random Access Memory. The history of small computers has been characterized by increasing amounts of RAM. The earliest machines had only 4K; most machines are now sold with at least 16K, and many users feel unhappy without at least 64K. What's it all for?

In the first place, the machines rarely allow the user all the RAM. Besides their own ROM, computers frequently eat into RAM for such tasks as running the disk drives, handling additional languages or connecting to peripheral equipment. A disk drive may consume 10K of RAM; a language interpreter another 10K. A page of graphics may require 8K, an animation 16K. At this rate, 64K of RAM disappears fast.

Furthermore, as users become accustomed to their machines, they begin to want simultaneous processing. When you start using a word processor, you find it's a wonderful time-saver. But after you've typed in your text, you must wait while the machine checks spelling. Then you must wait while it prints out your pages. You forget that the whole procedure is many times faster than you could ever do it before. All this waiting around for the machine gets on your nerves. You start to wonder why the machine can't simultaneously check spelling and print out while you keep typing.

Or if your working with graphics, you wonder why you can't have more detailed images, in more colors, drawn faster. If you're programming, you want more English like languages.

Whatever the reason, you end up wanting more memory. And machines with 512K to 1000K of RAM will be commonplace by the mid-1990's.