Let's say we are in 2$/4$ no-limit holdem and our opponent goes all-in all the time when we are in the BB. It's a heads-up match and there is 40$ in each stack. So, our pot odds when this happens are:

Pot odds = risk / risk + reward = 36$ / 36$ + 44$ = 45%

So we would have to play hands with at least 45% equity. That is the optimal strategy against this opponent. We would risk just more 36$ to win 40$ and the 4$ BB we put. We don't have to count the BB we put. But why?

Let's say when he goes all-in with all hands, we just receive hands that have 47% equity. We still have the advantage. The EV would be:

EV = %win*reward - %lose*risk
EV = (47%)*(44$) - (53%)*(36$) = 20,68 - 19,08 = +1,6$

So, this being a +EV play, GTO says we would have to always call this shove in this situation. But this is not in terms of profit.

If we are in a heads-up game and our opponent is always shoving with any hand, we are getting 1 to 1. We are risking 40$ to take a profit of 40$. We are risking 36$ + 4$. But the math in poker says "if you put anything in the pot, it is not yours anymore. It belongs to the pot". However, when you lose, you actually lose what you put in the blinds and the calling shove.

Let's say you are in another heads up match but you receive just 50% equity hands in the SB. In this game you and your opponent have always to go check-check. This is the rule of this game. Your opponent doesn't know you both are receiving always 50% equity hands, but you do. According to the pot odds math you are getting the right pot odds when you get hands with 50% equity because you have to risk just 0,5bb to win 1,5bb. So you are risking just 25% meaning you have to have hands with at least 25% equity. But you have more than it. The EV would be:

EV = (50%)*(1,5bb) - (50%)*(0,5bb) = +0,5bb

But again, when you lose, you lose the BB and what you risked.

So, in terms of profit that doesn't make sense. It is like risk 1 unity to win 1 unity when you have 50% chances of winning in a flip of a coin. You will never get a profit nor a loss because the EV would be 0. Hence, the first example of our crazy opponent going all-in with any hand when we are in the BB would be wrong because we actually would have to call his shoves with 50% equity hands or more to get a EV = 0 to the 50% equity hands and +EV with higher than 50% equity hands if we look at it in terms of profits, not pot odds. The EV in terms of profit of a hand with 47% equity would be:

EV = (47%)*(2$ bb + 38$ all-in shove) - (53%)*(4$ bb + 36$ call)
EV = 18,8$ - 21,2$ = - 2,4$

So my doubt is: Why don't we count the odds refering to the profits? Why do we have to assume that "what is in the pot belongs to the pot"? Thanks in advance.

You are counting the BB he put in.

If you call $36 and win you collect $80
If you call $36 and lose you lose a further $36
If you fold you lose a further $0

As you say your EV is calculated as:
-$36 + 47% x $80 = $1.60
(I didn't check your calculation but you seem to have got the right answer)

"So, this being a +EV play, GTO says we would have to always call this shove in this situation." - Correct.

"If we are in a heads-up game and our opponent is always shoving with any hand, we are getting 1 to 1." - Incorrect. Blinds skew this slightly.

Looking at your check-it-down BVB calculation your EV is:
-SB + 50% x ( BB + SB )
i.e.
-0.5BB + 50% x (1.5BB)
i.e.
+0.25BB
This is not what you have above, it looks to me that you have counted the SB twice in your calculation.

"So my doubt is: Why don't we count the odds refering to the profits? Why do we have to assume that "what is in the pot belongs to the pot"? Thanks in advance."

You are counting the pot odds on the decision, not on the hand as a whole. As I said in the first paragraph there are 3 possible outcomes
Call $36 more and Win $80 total
Call $36 more and Lose $36 more
Fold and win/lose $0 more.

I think you are asking why does the 80 include the blinds, but the 36 doesn't?

The reason is simple.

What if the house paid the blinds each hand... i.e. the $2 + $4 was actually put into the pot by someone not at the table. Would that affect your EV or pot odds? I hope you understand the answer is no. At the point you are making the decision, the only thing you care about is
- how much more you have to put in to call ($36)
- what total you will drag if you win ($80)
- the hand(s) you are up against and the equity you have against it (47%)

Nothing else matters, including who put what in the pot up to now.

All right. This will be very useful in studying pot odds. Thanks for your explanation friend