I've been reading about subnetting on a few stack exchange sites and others that I found online but the majority of posts seem to contain outdated responses such as class networks etc.
So to my knowledge, subnetting is used to make traffic easier to direct to the correct place which lowers congestion. This could be used by having a different subnet mask for each department in a business and if department A wanted to talk to department A then it would stay within the local subnet, otherwise it would look at the mask and determine where to send it instead of broadcasting it to everyone.
With switches, where traffic is only sent to the correct destination and not broadcast to everyone, is subnetting still needed? If so why?