Why do so many circleCI configs use `version: 2` for their workflows? I keep seeing this pattern around, and I haven't been able to figure out why people do it. I figure there's some dusty tome somewhere explaining why, or maybe just my google skills are off today, but can anyone tell me why so many people have workflows at version 2?
e.g. the example here, excerpt below
version: 2.1

executors:
  my-executor:
    docker:
      - image: buildpack-deps:jessie
    working_directory: /tmp

jobs:
  flow:
    executor: my-executor
    steps:
      - ...

  downstream:
    executor: my-executor
    steps:
      - ...

workflows:
  version: 2

  btd:
    jobs:
      - flow
      - downstream:
          requires:
            - flow

I figure I should probably be cargo-culting this in until I know why people do it, but I dislike doing that without any understanding :)
Thanks!
The Workflows version field was used to issue warnings for deprecation or breaking changes during v2 Beta, and it is deprecated as of CircleCI v2.1.
2 is the only valid number besides 1