If you used to need to use software for a weeklong project, you'd have to pirate it because there was no way to justify the cost.
Now you just sign up for a month and then cancel.
It's a huge improvement in flexibility and paying for what you use. Not to mention the software is always updated, so you don't need to worry about whether your image editor you purchased 7 years ago supports the RAW format of the camera that came out 2 years ago.