Why are people so unreliable?

I worked through an agency for a woman and she told me that she would love to have me back to work this Wednesday permanently every week. She said she would call the agency to let them know. The next morning, i called the agency to ask to have them set me as a permanent worker on the case but the agency said they have yet to hear a confirmation from her. Worst thing is I even dropped another shift with someone else on Wednesdays.

Another example, someone scheduled to meetup with me at a particular time/location but never showed up.

Should I just finally start going through life, not trusting what people say? Because this really isn't the first time people have been this massively unreliable

Why are people so unreliable?
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