Nothing is stopping you from creating diagrams, but UML is not required to create useful diagrams. Most concepts can be diagrammed using only boxes and lines.
This could only be said by someone who hasn't sat through their Nth architectural overview where half the time is spent defining just exactly what was and was not intended by a particular line+arrow between two boxes when a simple sequence diagram would have been crystal clear.
Both simple box+line diagrams and sequence diagrams are entirely dependent on the creator's skill at creating diagrams. I've seen plenty of confusing sequence diagrams. I guess it also depends on whether your team find it useful that diagrams depict low-level highly detailed interactions as opposed to higher level architectural concepts.
