A photographer sending client previews
You shot a wedding on Saturday and the couple is asking for a preview gallery before you've finished editing. You want to send full-resolution JPEGs so they can really see the work — but you don't want those previews ending up on Instagram before you've delivered the final edit and invoiced.
You drop the 60 preview JPEGs into the watermarker, type your studio name, set the position to Center with 25% opacity, and switch on Tile so it repeats faintly across each photo. Every preview comes back clearly attributed and useless for casual sharing, without obscuring the photography.
You email the gallery the same evening. The couple sees the work; nothing leaks; the final invoice gets paid before they get the clean files.