Someone wrote:
I need a formula that will show percent change from the
pervious month, the one I came up with is =SUM((D19-B19)/B19)

This is just one example of many that use =SUM() unnecessarily.
Presumably =(D19-B19)/B19 is just as good, if not better
performance-wise.

Why is this "screwy" idea so pervasive, namely using SUM() to
bracket any arithmetic expression? Is there a lousy text on the
market that is giving misleading instruction? Is this perhaps a
carryover from requirements of ancient spreadsheet software
(e.g. Visicalc)? (Not as I recall.)

I know: I shouldn't care. But I hate to see people learn poor
programming technique.