I think it's smart - You don't want someone else portraying your work as their own.

@ bepsf ...thanks, I noticed that very few do put names on their images so I wondered.

Houzz takes copyrights very seriously on the site, and always links back to your profile from photos what you have uploaded. Of course, one of the huge draws for the site is the beautiful photographs. When a watermark interferes with the visual enjoyment of the image, that image is much less likely to be featured within the app, so the exposure the person that uploaded it receives is impacted a great deal.