In order to function there needs to be at least 1 VLAN so by default ALL TRAFFIC is assigned to VLAN 1
(If you do nothing with VLAN configuration all your traffic is on VLAN 1)
As with all the default Usernames and Passwords for All Routers and Switches, everyone (Including people wanting to break into your network) knows this!
With that in Mind should you use VLAN 1?