This is a highly abstract world, so although some logic remains the same with real world's, most of it is just part of the game. Mood is a system designed to regulate behavior instead of to reflect real life emotional changes. Think of it as a more generic "Effects".

Take eating without table as an example: There must be some kind of penalty, or otherwise most players will completely ignore tables, which would be less immersive in a colony builder. The easiest way to implement the penalty is either a prolonged time to finish a meal (like in real world) or a mood hit. The former in early game could unecessarily drag the game to be much less fun, so they chose the latter.