[antasvara]

Just wanted to shout out the ability to copy, paste, and transpose the data using your mouse and keyboard. The ability to combine and reorganize data without needing to program is huge. It means you can grab data from an online source, paste your results into a report you're writing, quickly flip some data, etc.

Other commenters have covered the major reasons Excel is so popular. But Excel really shines because it's designed for business. I use R and RStudio for a lot of my work, and while it's great, there are little things that it can't do that Excel can.