I don't know anything about copyright and the law in India, but here in the U.S. it can be advantageous to put a mark on images for a couple reasons, most of which have already been covered, so I'll skip those.
One that often gets overlooked is that
IF an image has been registered with the US Copyright Office, and
IF that image has been used without the consent of the copyright owner, and
IF whomever used it removed the mark, it shows serious intent to violate copyright in the court's eyes. If they used it without removing the notice, it shows they were definitely informed and aware that they were using a copyrighted image, preventing them from claiming ignorance or that they thought it was in the public domain or something like that. So, either way, it's helpful to have marked it if it ever goes to court.
As copyright attorney Ed Greenburg says in this book,
Photographer's Survival Manual: A Legal Guide for Artists in the Digital Age (Lark Photography Book): Edward C. Greenberg, Jack Reznicki: 9781600594205: Amazon.com: Books , (paraphrasing) "
YES! It's
EASY to remove a copyright notice and most watermarks! It
WON'T stop someone from using your image without your permission!! And my wife
WANTS someone to remove your copyright notice, because she wants a
NEW CAR!!! Having someone remove your notice helps HUGE to prove intent of copyright violation in court!! So
YES, mark your images!!"
He and his co-author go on to say that you just never really know which of your images might be considered valuable or worthy enough for someone to use without your permission, so don't think your stuff isn't good enough or professional enough. Mark your images, file them with the copyright office, and then relax because you're covered just in case it ever becomes an issue. It's cheap insurance that you may never need, but if it ever comes up, it could be the difference between getting nothing and getting a pretty big payday out of the blue.
Though I register every image (that doesn't get deleted) with the US Copyright Office, I didn't use to mark them in any way, other than included copyright info in the EXIF. After reading that book and a couple others about US Copyright law and my rights as a photographer, now I do. It's very small, unobtrusive, easy to remove if someone wanted to, but I've decided that it's a good idea to do my small part to try to make it easier for my attorney and the court
just in case I ever need them to go to bat for me.
YMMV