Sequences are used for an organizational tool in your Workflows. There isn't a processing difference, but they allow you to group activities, so you could move all of those activities easily, disable them for testing, collapse them so you can viewer it more easily,  or just provide a descriptions and a name for that group, so that if you or someone else comes back to this workflow after a long time, you'll know what it does at a glance. 

In your example however the sequence is a bit redundant, because you can use the branches of the routing decision to group those activities already.