Thumbs Up

I finally got round to attempting the repair on my cracked phone camera glass. It all seemed to work fine though it was a bit slow and fiddly, and you need a hairdryer to melt and fully remove the old glue.
The success of the project was largely due to a very clear video posted on Youtube. That the man had taken time to record and edit a few repair stages and upload them is pretty helpful. I clicked the thumbs up at the end. Why would anyone click a thumbs down on such a video?