Each domain or a subdomain in your web hosting account uses, by default, the shared IP of the hosting server. Usually this would be sufficient and you would not need a dedicated IP for your domain(s).
The fact that your domains and subdomains use a shared IP does not affect their functionality in any negative way and the only side-effect is that you would not be able to access your website(s) by entering the IP in your browser’s address bar. But after all, we have domains so that we don’t have to remember IPs, so why would you need to be able to access your website using the IP anyway?
A scenario when a dedicated IP is not only useful but mandatory is when you want to activate SSL for your domain. To be able to install an SSL certificate for your domain you need a dedicated IP.
You can acquire a dedicated IP as an upgrade, as it is not included by default in any of HostCow's premium hosting plans.