Starfield was originally meant to contain more violence, but technical difficulties and a lot of confusion scrapped the idea

In a recent interview on the Kiwi Talkz podcast, Denis Mejillones, a former senior artist at Bethesda, spoke about the reasons why Starfield does not contain the same visual violence as Fallout 4. He noted that it was originally planned to include more violence, including beheadings, but technical difficulties made it too complicated.
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"It has a lot of implications for different elements of the game," Mejillones explained. "If you need to cut off a helmet in a certain way, it requires additional systems and considerations." He stressed that implementing such effects has become a "big mess" with many details.
Dennis also pointed out that even if the team was willing to spend more time on creating violent effects, it might not have been in line with the overall tone of the game. "For Starfield, we wanted a more restrained and realistic approach," he added.
Mejillones stressed that Fallout has its own unique style with elements of humour and exaggerated violence. While Starfield draws inspiration from series such as The Expanse and Star Trek, the approaches to violence and aesthetics proved to be incompatible with its subject matter.
Source: Kiwi Talkz