The first thing that comes to mind is because it's FREE--anyone can access it.
The second reason is it's easy to share and edit in real-time. Never have to wait on someone to get it, change it and send it back to you.
The next reason is Google Sheets has built in assistive features that help with formulas and finding insights into the data.
And finally, since it's part of a suite of tools, you can easily connect to other apps like Google Forms to collect data. And then share it by embedding it into a Google Slide presentation.