- Devices in the same subnet contend for the same resources, whether it be for airtime, ARP, DHCP, etc, so those still need to be at a manageable size.
- In addition, problems are frequently confined to the same layer 2 subnet, so if you use multiple subnets, if you have a problem with a single subnet it can be isolated and you still have the use of the other subnets.
- If you use a single subnet and you have many devices with static addresses, you have many more devices to change if you decide to make a change later.
Even if we can assure that broadcasts will not be a problem, multiple subnets offers the best flexibility to be able to manage a network, period.