-Write locks/file ownership. Bob maintains the master schedule spreadsheet and no one else is allowed to touch it. Mary gets given access and leaves it open and goes to lunch and Bob can't update it for the rest of the afternoon.

-Multiple sources of the truth. I've seen spreadsheets used in lieu of professional estimating tools for pricing jobs, and been abused because I wasn't use the "latest version" of the spreadsheet that got cc'ed around at 11pm called estimate July 24 v11a LATEST.xlsx

-Fudge factors and spaghetti formulas. You can take a nearly complete data set and essentially manipulate it to tell any story with inconsistent formulas, hidden columns, references from other sheets etc.

-VBA extends capabilities but is has some serious performance issues, doesn't implement objects correctly, doesn't handle errors well, code can't be version controlled.

-Gets used to do a poor job of purpose built software that the business has licenses for, like estimating/scheduling/MRP because of a lack of training.

-Business logic usually isn't apparent or documented and has to be reverse engineered to be understood.

-Propagates silos within businesses as they decentralise data and tend to diverge.