Why is it customary to put each vlan on a separate network?

Question

Computer networks

For example, we have 15 PCs with ip range 2.2.2.1 - 2.2.2.15, which are connected to the L2 switch. We need to divide them into 3 vlans. Why is this division considered incorrect?
2.2.2.1-2.2.2.5 - 1 vlan
2.2.2.6-2.2.2.10 - 2 vlan
2.2.2.11-2.2.2.15 - 3 vlan
Why is it customary to follow the rule "separate vlan - separate network"?

Answer 1

VLAN is to implement several separate networks in one physical. Giving them different subnets to set up routing between them - otherwise it won't work.
If these networks do not plan to access other networks or the Internet (routing is not needed) - for example, connect equipment to each other - cameras and a recorder, a machine tool and its control terminal. Then you can leave such addressing.