Work in fields like healthcare, governmemt, finance, law or defense and you will see Excel spreadsheets are used for just about everything. They are simple to create, simple to use and offer very advanced controls for a fraction of the time and cost it requires to development a sufficient framework for the data in-house or configure an existing solution.

It is very easy to train people on how to use excel if they are willing to invest the time to learn formulas, and once you learn VB, you will be tempted to do most data presentation in Excel.

That said, just because most people know how to use Excel does not mean they are technically capable of setting up things like version control, backups, validation or security. A lot of users I have worked with in addition get their files from someone else, who may not even work at the company anymore and they have no idea what is or could be running in the background or how exactly the calculation in certain cells is done. Further, it is very common that one technically capable person creates an excel that becomes a crux of an internal process simply because it is the easiest thing to use, once IT governence policies are put in place, it doesn't help because they damage lies in the fundamental data they started with.

Tl;dr it is more common and innocent than it seems.