First off, wrong forum. I believe this should be in gamer life or Pathfinder advice.
I have 3 theories to your question
The first is that of storytelling. People like characters, and origin is where it's at. This applies to me, but I'm sure it applies to others as well.
Next, higher levels are boring. It ends up being focused on what you can do rather than why you do it. You become a superhero with disregard to surroundings. This is why E6 was invented.
Third, a lot of people in the forums are new to tabletop and join because they can't find any enthusiast clubs around. A 1st-level game has the least rules and planning, so it captures a wider market.