An updated site always gives the user the impression that the site is run with great vitality and that the contents are constantly innovated.  This makes him feel that he is consulting a well-kept site where he will find support.

If, in addition, the texts are not only new but also interesting (news, for example) or the site contains frequent initiatives (for example, special offers for site users only) your clients/visitors will keep coming back to visit you.  This is what marketing experts call customer loyalty and makes you realize that creating a site is important, but keeping it updated is even more so.