I'd guess politicians only believe in the fact that they can say whatever numbers they want and most people believe the numbers are truthful and comparative. That's certainly not the case.
We live in a vibrant country. People want to move here. We have a growing population. We have a growing work force. Oh, wait, not according to the federal agency that publishes unemployment numbers.
See, they have a number they basically make up called the "Labor Participation Rate". The number isn't made up, but how it's derived is, and it changes to suit the message politicians want to spread. See, if somebody doesn't want to work, or decides to stop looking or goes on disability, they aren't considered unemployed! It's like magic! One day you are unemployed, then a day later you hit a threshold and now you are considered to not be! As of now the Labor Participation rate is 63%. That's rather low compared to history.
You'll also notice, if you follow that sort of thing, that most weeks the unemployment numbers are announced. Then a couple days later they are adjusted to be worse. Then the next week they announce the numbers (based off the adjusted numbers, of course) then quietly again they are adjusted to be worse than announced. This happens most weeks. We get the impression that the job market is improving faster than it is if we just pay attention to the headlines. When you start to look at the actual data, the pictures is much less rosy.
I urge you to do your own research on this topic. It will, unfortunately, hurt your faith in both politicians and the news you hear and read, but it's far better to understand the truth, and to understand how you are being lied to.