Because they need to observe two things at once.
The Resident Evil 2 1-Shot demo was announced on Tuesday and the complaints about the 30-minute time limit has been flooding the Internet since.
PC gamers with mid-end specs stressed that 30-minutes isn't enough time to both benchmark their performance and enjoy the gameplay.
This is why I'm going to spend most of my time benchmarking my performance on the PC (Steam); followed by replaying the demo on the PlayStation 4...
The demo will be released on January 11, 2019 for those platforms along with the Xbox One.
Image credit: Capcom