Less work for the NC developer to tweak the appearance of the embeds, because we can batch-change the appearance from our Vimeo settings.

There is more information / functionality immediately available to the user than just playing the video, (NC link, title link, share link)

For older / less experienced users the progress bar at the botttom more obvious that this is a video to click on.

Avoids play icon showing up on someone’s face.

The naked embed may result in better/more dynamic UX for when the embed is resized on different screens/devices. 

Cleaner look.

Control over the appearance of the font, and can make it match site style. (Text and/or play icon can either be burned into jpeg or overlaid by developer.)

Reducing the user’s options to only one (click play) may be simpler.