I am not sure but maybe the people who later might help this company or required for its success - future VCs, top talents they would want to hire, press coverage and all - might be influenced by the YC tag and it might work for Piggy in this way. And the YC networking as they say.
I do think it would help in hiring tech talents and maybe also with raising future rounds at high valuations. I know more about the first than the second.
Also it does make me happy to see more Indian startups being a part of YC.