On 5 November 2013, The Complete Series 1-7 Blu-ray was released marking the first time Series 1-4 were released on blu-ray. In NTSC, DVDs are 720x480 and in the UK it's 720x576 PAL. Blu-ray releases benefit the US market and BBC Studios were releasing them but never shipped them out. Then, on 2 October 2018, they released the entirety of the 9th and 10th Doctor's era on DVD. This opens up an opportunity to release the set on Blu-ray, but not without demand. If you want the set on Blu-ray then petition now!