They do. Some people don't use them; and (if disciplined) use one or more worksheets to store data and refer to it purely internally and (otherwise) just sort of ad-hoc mix data and formulas.
In some cases a database connection is where the data comes from; but the number of cells grows because it's conceptually easier(and in practice often less opaque, given the ugliness of displaying very large cell contents) to munge on the data step by step rather than trying to ram everything into one transformation.
Coming from the IT side; and having to field questions from the perpetrators of some absolutely hideous excel sheets from time to time(no, I didn't even know that there was a way of creating a type of embedded image that actually quietly triggers the print spooler subsystem to do something that generates a new image based on the contents of another region of the spreadsheet, still don't know how they did that; but it's objectively depraved) I understand the hate; but I do have to admit that spreadsheets are pretty good for napkin-math thinking-it-through type processes.
Like when you work it out on paper; you've got your input, then you have a cell with the contents of the first transformation you wanted to make, then the second, then the third, and so on, and at each step you can think "does this value make sense?"
It rapidly gets out of hand in quantity; but as a rapid sketchpad for thinking something through you could do a whole lot worse. It's also tempting(again, tempting down the path of darkness in quantity) for dealing with jobs that need both a bit of string munging and a pretty-printed output.
You send the intern down to storage with a barcode scanner and have them start snagging SNs and MACs and stuff from the shipment of new gear. Turns out various vendors use different prefixes on different barcode values to inform their own ERP/inventory system/warehouse people which of the 5 closely spaced barcodes their scanner hit. And each vendor uses a different set of conventions, and while obvious enough they aren't documented. Ok, no problem; intern comes back with raw list; all the Lenovo SNs get a 'last x characters' substring; all the Cisco MACs get another transform, whatever.
Obviously if it were your inventory/warehouse system you wouldn't be treating the barcode scanner as a raw HID device and doing ad-hoc transformations, there would be a program that automatically uses the prefixes to populate the correct parts of the form; but you want to stick your head into ERP project hell rather than come up with maybe a dozen lightweight string manipulations? Obviously, you could also do it in your choice of scripting language and iterate through one CSV to create another; but that mostly just conceals what you did from anyone who doesn't use that scripting language; while you can walk basically anyone employable through the logic of the spreadsheet prettifying.
