It is very simple: Poker is not always a game where you have a big edge. Maybe once in a while 0.3% make the difference between a good call and a fold. You want to use and calculate every tiny edge, so you should know about how to calculate odds in theory.

Of course - at the table you can most often use the outsx4 or outsx2-version to calculate your winning probability for two or one street.

By the way: if you got an open ended straight flush draw with K

Q

on a board of J

T

7

7

against 2

2

you will have 25 outs against your opponent. The formula gives you 50%, but in fact you have 56.8% -that is not a marginal difference!

For programs that show you pot odds: be careful, some poker rooms don't allow you to use those programs. If pot odds are shown then it might be that it assumes that you bring a single bet of one big blind. Otherwise you should consult the handbook of your program or disregard the message.

hope that helps