Because it's not a raw image instead is placed here: https://mars.nasa.gov/mars2020/multimedia/images/

The same images were posted to the official Twitter account: https://twitter.com/NASAPersevere

It's pretty normal for NASA/JPL to release the coolest-looking pictures as quickly as possible for PR, and then follow up with the comprehensive releases of raw data later, especially in the early stages of a mission. I don't see anything to indicate that BBC was given any kind of special treatment.

I was praising the big steps that NASA is making on this mission to really be publicly accessible... But they don't really have a unified communications plan. Images and information are spread out on various sites. The general public can't be expected to go searching. I was hoping the raw image site would be the primary location for all mission photos.

this also frustrates me