True you can waste time equally at home or in the office, but that's not the only consideration.
For WHF to be totally effective, the employee needs to be a sole contributor, has mastered their position, has easy-to-measure performance metrics, and is not looking to be upward n their career.
Anyone that is developing in their role, working in a team, performing leadership duties, or looking for career advancement will not be as successful or valuable in WFH.
Large companies, also have to deal with other things: Fairness - can't have some at home and others in the office; people and leadership development are slower for WFH, as are the cross pollination of skills, corporate navigation, and networking -- all needs of a business.
But I think the big one is productivity. Initially, WFH showed productivity improvements, particularly for big companies. Absenteeism went way down, and focus way up. I know a large employer that went from 14 absent days a year to 3 during the pandemic. WFH slowly drifted back to 14 days, and productivity is declining below pre-pandemic levels mostly because employees are taking considerably longer to develop in their roles.