If a problem involves a lot of formulae that are identical except
that they each apply to a different point in time, MM allows
to write just one formula for this:
profit[t] = income[t] - outgoing[t].
Conventional spreadsheet development requires a separate formula
in each cell, either written by hand or generated by a macro or Visual
Basic program. Writing multiple formulae by hand increases the
chance of errors. Using a program to generate them makes
the model less readable, since you need to read not the model itself,
but a program that generates it.