Additionally as can be seen in almost every few episodes....raising ones shield is generally seen as a combat move / aggressive move. All races do it only whenever a battle is imminent.

The federation in contrast to most other gerater empires is one of exploration and peace. Thus them flying around in half combat readyness is not something that tells people "we come in peace." but more "get ready whenever our sensors detect you we will attack you.".

If we compare permanently having shields with modern day ship warfare....you could say "the federation ship has their ecm set to full and a target lock on us.....BUT their weapons are not ready...yet."

Thus energy consumption aside, it is not something the federation wants to do because it projects the wrong image about them and their intentions.

As can be seen almost every few episodes, raising one's shields is generally seen as an aggressive move. All races do it only whenever a battle is imminent.

The Federation, in contrast to most other greater empires, is focused on exploration and peace. Flying around in a state of combat readiness is not something that tells people "we come in peace" but more "get ready, whenever our sensors detect you, we will attack you".

This is directly supported in Star Trek: The Motion Picture through this exchange while the Enterprise is approaching V'ger:

CHEKOV: Should I go to battle stations, sir?
KIRK: Negative, We'll take no provocative action.
DECKER: Recommend defensive posture, screens and shields.
KIRK: No, Mister Decker, ...that could also be misinterpreted as hostile.

If we compare permanently having shields with modern day ship warfare, you could say "the Federation ship has their ECM set to full and a target lock on us, but their weapons are not ready, yet."

Thus energy consumption aside, it is not something the Federation wants to do because it projects the wrong image about them and their intentions.