Why do you need to watermark photos and images on websites?

Question

Copyright

Why do some sites put "watermark" tags on their photos and pictures? What practical meaning does this have? Type:
Or:
This does not, in theory, make the picture unique.

Answer 1

So that mom's web designers can't steal to their site.
So that, even if they steal, they advertise the source site.
Well, to change the hash amount of already stolen.

Answer 2

There is one more option. On someone else's site, just img src = from your site.
Those. You act as a free hosting of pictures for someone else's uncle. Imposing the name of your project is
more profitable (no advertising) and easier than preventing such use.