This has many practical applications. A favorite one is shopping carts. Few of us want yet another password to remember, and having to bookmark a special URL can be troublesome, especially if your bookmark file gets trashed when you upgrade to the latest browser version. Cookies allow such a site to leave the information attached to your browser so you can quickly get back in. The arguments range from concerns about the use of valuable disk space to paranoia about government oppression.
Disk space is a minor concern.
The number of cookies a browser can store is limited. The cookie specification calls for a browser to hold a minimum of 300 cookies. Each cookies can be no larger than 4 kb and no more than 20 cookies can come from any one domain. In this day and age of multi-gig disks, that seems a small price to pay for the convenience. We're all told to forget our concerns about information security.