In some cases, mistakes are just part of the work and even professionals make imperfect joints. In other cases it is rushed and part of the character of the show (Roy). In most cases though, I believe they are only taking the care needed to prove the method and intentionally aren't shooting for perfection because videos of this nature are targeting beginners. Beginners usually want realistic, achievable standards and probably don't want to be discouraged by seeing perfection at every turn.
If you are watching more advanced stuff or professional project-level demonstrations of commissioned or paid work, you will see a long series of videos where a lot more care and explanation of how to avoid problems occurs.
Now, if you paid for the video and the production quality and narrative is poor, I could see a complaint. Otherwise click on by.