Why are the US time zones not straight?

Related questions

1. What time zone is CET in Europe?
2. How far is CST behind GMT?
3. What does 2pm CST mean?
4. Do Clocks go forward in Europe?
5. What time zone is 2 hours ahead of Central?
6. What states are CST timezone?
7. Which country celebrates New Year's Day all year round?
8. What is CST time in USA?
9. How many time zones does Russia have in 2018?
10. Do Clocks go forward or back?

Tags

1. #zones
2. #boundaries
3. #political
4. #other
5. #national
6. #actually
7. #simplification
8. #straight
9. #often
10. #considerations
11. #idealized
12. #earth
13. #because
14. #lines
15. #always
16. #follow
17. #vertical
18. #illuminated
19. #round