Bethesda claims that developing the game for a single platform has benefited them.
We have known for a long time that Starfield is a game that will be released on Xbox and PC, the Xbox version being the only one to take place on consoles. Obviously, a big part of the decision to make Starfield exclusive came from Microsoft buying Bethesda.
The purchase caused plans to completely change with game developments like Starfield and others, therefore we have this game exclusively for Xbox and it will not be released on PlayStation. For Pete Hines from Bethesda, having developed the game for a single platform was an advantage, since he even thinks that he had to work on several versions, the game would not have been marketed this year.
Starfield on PS5 would have caused the game to lag
I really don't think Starfield would have come out this year if we had to develop it on a completely different platform than the current one. Focusing on fewer platforms has been a huge plus for our development team. Creating a similar game on multiple platforms would have involved much higher risk, as well as additional development time and higher costs.
If all goes as planned, Starfield will be available on Xbox and PC next September, remember that the game will also be launched for Xbox Game Pass.