[adrianhoward]

Because it's more effective not to (in my experience anyway). Instead use the same numbers and make it look like a great deal. So rather than.

"Your bill is $10k, pay after Dec 15 and you get fined an additional $5k"

say

"Pay by Dec 15 and get our discount rate of $10k, otherwise get our standard rate of $15k"

Numbers are the same. Very different reaction from people.

Discounts are something people want. Having time-limited discounts is a classic sales technique. People don't want to lose out.

Some departments are required to take discounts, but encouraged to fight late fees.

Fines are annoying, but the effectively give you a structure and excuse for doing the bad thing.

There is no logical difference - but people aren't logical.