You want to know that if anything is wrong - you can get help or even get your money back. If it is something that could require repair, you want to know you have good service available. You want to know as much about your vendor as possible. Of course you want to know that you can trust vendors promises. On the other end of the spectrum are those telling too little or nothing at all - and that hurts their business just as much.
People do that because they think they inspire trust in their visitors.
Actually they do just the opposite and hurt their business in the process. Sadly, by making this false claim they make all their other claims unbelievable. Tell them the truth about yourself. It is called self-disclosure. Don't be afraid of being vulnerable - people will really respect you for admitting your flaws.