Depends. Vlan’s separate the network so do you want to separate the network for any reason?. Maybe for security reasons or for sizing purpose (is your network growing bigger than you expected?). Most people that create Vlans do it basically for these two reasons, amongst many.
Hope this helps
Agreed – the best reason for segregating traffic is 1) for security, 2) to group like users/applications aND 3) Scalability / control of growth…