You can, if you download the Windows 8 Media Center extension. It's free until the end of January 2013 if you already have Windows 8 Pro. Upgrading from Windows 8 to Windows 8 Pro (if necessary, you didn't write what edition of Windows 8 you're talking about) isn't free, alas.
http://windows.microsoft.com/en-US/windows-8/feature-packs tells more.
PS. Only the marketing and sales department of Microsoft know WHY they didn't include it.
why can't i play dvd with win 8?