I spent a lot of time trying to understand why Gorky - and others playwrights - would bother adding such a small character in their scripts: why waste precious stage time or make the play even more expensive to produce? Of course, there is representing the working class in the world of idle bourgeoisie (Summerfolk is set a few years before the Russian revolution). Also, the importance of sticking to reality: these characters wouldn't have prepared tea themselves.
But as rehearsals advanced and the acting became more precise, I also realised how the play could not be without the servant role:
Changing the course of action
by coming in and out, I give the main characters/ actors, a pause, a time to breath and change their mind... thus changing the course of the discussion of events. They are about to explode and fight - then tea arrives and everyone calms down - giving the audience a glimpse of the characters' feelings but not allowing events to unravel.
Giving flavour to the relationships
By announcing characters differently - the mistress' best friend or the master's untrusted assistant - I give the audience context about the relationships, and colour the whole play.
Crazy, the responsibility on my shoulders now....