Sitemap is helpful in any way for promoting a portal
I want to ask that is sitemap in any way helpful in promoting a portal. I have news portal in Indian language on WordPress and wherever i go to get my portal developed in php they always ask me that do your website have a sitemap. I want to know that how a sitemap is helpful in promoting a portal. Is it really necessary that my portal have a sitemap or its just a new money-sucking thing which is too much highlighted by the developers. Please help.