As a programmer who had used Excel for years, seeing my accountant start typing a formula, change sheets, select some cells, go back, repeat, was a learning process. I didn't even know you could do that, and also, I hated it. But it worked very well for him.

I've more recently been exposed to a few spreadsheets that are used to calculate quotes in major insurance businesses when I was asked to create an online process instead, replicating the questions and formula.

They're things of horrifying eldritch beauty. I seem to always find at least one error, and no one I'm allowed to talk to ever really knows how they work since they're built up over years. Those dependency arrows are a life saver.