1. there is a base load of meetings, admin, interviewing, chore, etc that is not reduced when total hours are reduced, and so what gets reduced is the high valu

1. there is a base load of meetings, admin, interviewing, chore, etc that is not reduced when total hours are reduced, and so what gets reduced is the high value work. you can't hire people to do this stuff as they can't make decisions for you, or interview for you, etc... this base load is part of your job 2. there is a base load of cost from each employee in the form of legal, pension/tax accounting, payroll, HR team, desk, office, equipment. whilst you could argue 4 people doing 40h weeks is equiv to 5 people doing 32h weeks you're also increasing the base cost by 20% across the company 3. hiring people is hard, now we've just made it that we have to hire 20% more people for the same effort, increasing the admin base load further too. (although the counter argument to this is that you're better positioned against low performers who have less impact, but then, maybe you end up carrying low performers longer as now they're less visible) 4. on-call... you probably can't reasonably construct an on-call schedule that works for all by mixing 40h and 32h people on the same team... so now you're starting to have the decision forced on the 40h people too, who now only earn 80% of what they earned and their circumstances may mean they do not want to. 5. RSUs / stock, you probably can't reduce the what someone already has, can't take it to 80% of what was in the contract, you probably only get to do this to new people joining (but see #4, you'd have to do the whole team at once and hire based on this, and probably can't mix it with the 40h people) 6. if you have offices, this forces you into a hybrid working situation as you can't seat everyone... you cannot even bring everyone in on any given day... unless you massively increase your office cost, or go fully remote (I'm in favour of full remote and it's what we do at where I work, but I know the World apparently does not agree) there's lots of reasons, but the biggest may simply be: change is hard, better to start with this... but starting with this is also hard as the chances of you succeeding with few heads and less effort (time) is against you.