I have the impression that almost all English native speakers use the expression not a) but b) when they launch a meeting, presentation, etc.
a) Let's start.
b) Let's get started.
I have two questions.
1) Is a) a correct sentence?
2) The reason for the use of the verb "get" in b)?
I suspect "get" makes the voice of the sentence passive, so that allows the speaker to omit an objective.