Steemit 101: Help me clear things up.

Hi guys im a new member here, and i just wonder,
Why do shitty post with shitty contents get upvoted and trend, i mean like the posts that doesnt even benefit you, posts that isnt even interesting or posts that isnt even useful or helpful?

And why do the worth of your post falls down as day passes by? Like for example youve got upvoted by 26 people and its worth $1.33 but in the next day it becomes $1.05.

Please help me clear things up steemians this might also help new members to understand the platform very well. Good Day and thanks.