If you are trying to market a product or yourself you need a domain name to appear even half way serious. I am many non-sellable interests and set up sites related to them on subdomains or on webspace provided by my ISP. The latter idea is inadvisable if you ever desire to upgrade and use a domain name with web site for basically you have to await to be reindexed once again and try to get those linking to your site to change backlinks.
Mainly for three reasons: 1) To develop a unique website around it. 2) For Investment or speculation (including parking, mini-sites). 3) To protect your TM.
In the past, all websites are known by their IP address like 234.213.131.144 which makes it difficult to remember the website address. Computers can understand that but not humans, at least not normal ones. It used to be like giving someone the coordinates in Latitude and Longitude. I mean you can say you live in 24° 33' N 81° 45' W but who would know where that is ? Then someone smart came out with the idea of Domain names which specifies remembering the website location by giving it a name, a domain name. This will come will a simple name to remember like http://www.digitalpoint.com . By the way, 24° 33' N 81° 45' W is Key West. I supposed if you tell someone you stay in Key West, it would be easier for people to know where that is.
Woah! Nice one dude... this explains his question well . how difficult it would be memorizing so many IP's now