Videos when they are made are much cheaper to produce than photo galleries. When a video is made, the company making the video pays a one-time salary to a videographer. As a result, Mindgeek owns the videos outright under the brand that it is under, i.e. Brazzers, Mofos, Digital Playground, or Reality Kings. When a photo gallery is produced, the company ordering the accompanying photo gallery has to to pay out royalty fees to the photographer whose pictures are displayed at the website. This continues as long as the photos stay up on the website. When Mindgeek's webmaster delists an adult model or pornstars' content and the pictures are taken down, then the royalty payments cease. That's why you have so many scenes over at the Mindgeek controlled sites without accompanying picture galleries. Most times though, if a scene fails to load then both the photo gallery and the video are taken down. They just don't fix or repair them or even remaster them. Try looking for an old Audrey Bitoni, Carmella Bing, Holly Halston, Shyla Stylez, Savannah Gold, or Sienna West scene. Probably not there at Brazzers. As they were taken down long ago.
As for server space, actually when the servers got overloaded at Brazzers, Reality Kings or Digital Playground, Mindgeek's webmaster used to bring over full movies to Pornhub Premium (the subscription paysite) while partial videos would be brought over to Pornhub (the free tube site). Pornhub's servers are twice the capacity of Brazzers, Digital Playground, Mofos and Reality Kings combined. That process ceased in late 2018 and was intensified when the G-D-P incident came about. Mindgeek wants to avoid third party lawsuits at all costs.