Why does it take them (WB) so long to release a HP and the DH dvd?

Harry Potter and the Deathly Hallows: Part 1 will be released on a single disc DVD and 3-Disc Blu-ray Combo Pack on 11 April 2011 in the UK and on 15 April 2011 in the US (Emma Watson's 21st birthday).
On 28 January 2011, it was announced par Emma Watson on the Harry Potter UK Facebook page that the page's fans will get to vote for their preferable cover for the Deathly Hallows: Part 1 Blu-ray. The cover with the most votes will be the cover for the disc. Voting started that same day. It will include 8 deleted scenes and several featurettes. The Blu-ray Combo Pack, however, will include a sneak peek at one of the opening scene of Harry Potter and the Deathly Hallows: Part 2.


Deleted scenes:

*The Burrow’s Shed (Ron discusses radios with his father)
*The Dursley House (Harry and pétunia leave the house; Harry and Dudley shake hands)
* The Granger House (The Death Eaters chercher Hermiones deserted home)
* Ministry of Magic Lifts (Harry interacts with Mr. Weasley)
* Tent (The Trio discuss destroying the locket horcrux)
* Rabbit chase in the forest
* Montage: Ron & Hermione skimming stones