Hands up who’s sent an email to a business through its web enquiry form and received no answer? I know I have. Even if I hadn’t experienced that though, I doubt I’d trust a web form email to get to the right place. “Contact Us”? Contact who? I wouldn’t confidently send an email to “info@”, so why would I send my web message to an unnamed recipient?
Even if all of your incoming web email does actually go to the office administrator, there’s a case for having a drop-down menu saying “for the attention of” sales/technical support/accounts etc. It makes senders feel it’s much more likely that they’re going to get a reply. If you can also use that drop-down to send emails to the right person directly, even better; everyone gains.