My perspective:

- Purchasing

- Downloading

- Installing

- Patching

- Commitment

- Mechanical Skill

It allows you to experience the story of a game or the experience of high skill play with little up-front cost or long-term commitment.

One you've left out: hours wasted farming experience or searching around for whatever you're supposed to do next tend to just be cut out of let's plays. (You still need to suffer through those if you're watching a stream; the advantage of a stream over an edited video seems to be mainly that it provides a social group to hang out with.)

Paying for the game, and in some cases the console it runs on.