I think the OP asked the question in the wrong way. I think they meant the ORIGINAL pot (I believe that is called the main pot). It is very surprising that this change has not come about for a few reasons.
One is that you put in the NECESSARY risk to win that pot. That should be enough. But there is another reason, which I will call gamesmanship. Now, guile and bluffing and dastardly play is part of poker, but let me give an example of a case where we really should change this rule.
Assume there is some good action preflop, and we have one player all in, and there is 6000 in the side pot, and 50K in the main pot. One player bets the minimum, 4k. The other player almost HAS to call for the main pot no matter what he has. On the turn, again, we have a min bet of 4k, and again, almost HAVING to call (hopefully, everyone understands the context of my word "having"). On the river, the person betting 4k now bets 30K and gets a fold. The bettor won 8k from the other caller KNOWING he HAD to put in those bets on flop and turn, and FIGURING he needed a big hand to call.
In other words, because of these archaic rules (to put it politely), the bettor was in a position to FORCE a call that MAY NOT have necessarily been made. The dynamics have changed from the way normal risk/reward should work.