Citigroup is spending £1bn to attract staff back to its Canary Wharf tower. Maybe it’d be easier to provide accommodation — it worked at Bournville after all
To actually address the question, it’s because commercial buildings don’t (generally) meet residential building code requirements, even if there’s a kitchenette and a shower, etc. They are simply not meant for the same purpose or to be occupied 24/7 unless they were engineered that way from the start, which is exceedingly rare. A lot of office buildings have floor-to-ceiling windows and complex HVAC systems simply to make sure people aren’t cold, breathing stale air, or too humid/dry, so they also use a lot of energy.
To actually address the question, it’s because commercial buildings don’t (generally) meet residential building code requirements, even if there’s a kitchenette and a shower, etc. They are simply not meant for the same purpose or to be occupied 24/7 unless they were engineered that way from the start, which is exceedingly rare. A lot of office buildings have floor-to-ceiling windows and complex HVAC systems simply to make sure people aren’t cold, breathing stale air, or too humid/dry, so they also use a lot of energy.