So i was wondering does ki suppression drain energy from the user, since they always need to think about this and maintain focus to some extent.
To start things of we know that not everyone can hide their Ki since it is a skill that has to be learned. We saw an an example of that when the sayajins arrived on earth and were surprised by the fact that the earthlings could control their power level and change it on will. Later on Namek, we saw that people are able to track down others who are unable to do that, that is why Dodoria and the others are always "powered up", and why the scouters were able to read their true power level ( i am not taking transformations into the account here).
Usually one of the common reasons besides trying to stay "low", is said to be to preserve energy but if you take into account the examples i mentioned above, that would mean that people are constantly losing energy without doing anything, which seems totally illogical. Even if that was the case somehow the loss should be minimal.
Taking everything into account there just does not seem to be a reason to do that, besides if you want to hide yourself on purpose. I doubt this was anywhere explained in depth, or that there will ever be a 100% verified answer but i would like to see what others thinks about this.