Why do wants and needs influence our perception?

Wants and needs is predominantly caused by brains in order to fulfill what our body considered missing. In order to fulfill this, our brain tend to give signals that make us focus to make that fulfillment before we could move on to others.

Because of this, our perceptions tend to be catered in order to finish this fulfillment. (for example, starving people may create a perception where they see anoher objects as an actual food)