system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did the US tax code become this complicated?

Thinking about April 15 coming up, and the entire multi-billion dollar industry that's sprung up around tax preparation, tax evasion, paying as little as possible, etc. I think back to 100 years ago, and I can't imagine life in 1915 re: taxes being this complicated. Even less so 100 years before that, when we probably just dropped some coins off at the post office or something (who knows). Is there an ELI5 answer to the evolution of the tax code, and how/why it became necessary for the IRS to be so complex?   
  
**edit** April 15 is tax day, April 4 is my parents' anniversary.
gpt
What started as a simple system had extra rules grafted onto it over the years to help out various special interest groups, government program and to influence people's behavior without passing overbearing laws.  Add 50 new rules a year for 100 years and pretty soon you got yourself a whole mess of rules.