Bosses may want people back where they can see them work, (as if results dont speak for themselves)
Some employees will produce less with WFH, and simply do better in the office, free of distractions/temptations. Some are interested in WfH specifically so they can multitask (e.g. child care) and will be less productive than in-office workers.
Employers might advertise a job as WfH, but when the results are sub-par, employees faced with coming into the office or suddenly losing their job (at an inopportune time) will overwhelmingly cave to the demands. Without unionization, employers have a heavy advantage over the preferences of their employees.
How long until employers decide WfH is a perk worth 25% lower salary?
How long until employers decide with all the WfH staff, they can just go further afield and employ cheaper Romanians (still an EU country), or Indians, or similar?