Why does the author include a soliloquy in the play?

the flight of the vulture

characters:
vulture, male
flight attendant, female
pilot, male
man, standing at the back of the line
woman, wearing a fox stole
passengers, forming a line

(people are calmly standing in line with boarding passes in their hands. flight attendant enters stage left. she approaches the front of the line.)
flight attendant: (in a falsely cheerful voice) we are now ready to board for flight 5b. have your boarding passes ready.
(the line begins to move forward. suddenly, a chain reaction of gagging and screaming starts from the back of the line. the people in the back of the line are looking off stage right.)
flight attendant: what is it?
(a vulture enters stage right. he is carrying several beat-up, old stuffed animal dolls with him.)
vulture: (to last man in line) excuse me, sir. is this the boarding line for flight 5b?
man: aaack! you are carrying around dead animals! that's disgusting!
vulture: i brought them as an afternoon snack.
(the people in the line react more violently than before. the sound of their gagging fades. the lights dim and a spotlight hits the vulture.)
vulture: i guess i can't blame them. this is the reaction i get everywhere i go. (sighs) it's hard for a vulture to make friends with humans. humans have called me ugly, gross, disgusting. the list goes on. i've stopped trying to reason with them. i tried to explain that i was just made to eat animal carcasses. i don't know how to make them understand. i don't act rudely when i see someone eating fruit. all i want is a little respect.
(the gagging sound begins again and lights come back up.)
man: go away! no one wants you on this plane.
flight attendant: (approaching the vulture, holding her nose) sir, you are creating a disturbance and bothering the other passengers. i'm afraid that i cannot allow you to board this plane.
vulture: but i bought a ticket like everyone else.
woman: if he gets on that plane, i am going to sue the airline for undue distress. i can't believe he wants to bring dead animals on the plane. dead animals are disgusting.
vulture: (to audience) someone needs to tell that to the little guy draped around her neck. (to flight attendant) well, if you don't let me on, then i'll go to the aclu and sue the airline for discrimination!
flight attendant: oh no. umm . . umm.(pilot enters stage left.)
pilot: what is taking so long? we are on a tight schedule. let's get this plane . . whoa, what's that smell?
(all the people talk at once and point at the vulture. the vulture droops a little. the flight attendant runs to the pilot and grabs his arm.)
flight attendant: we have a big problem. this vulture bought a ticket and wants to board, but his "luggage" is causing a commotion. what should we do?
pilot: (approaching vulture) i'm very sorry, sir, but you cannot get on the plane with those. (points to stuffed dolls) the airline's rules are very clear. (clears throat and speaks as if reciting a memorized passage) chapter 4, section 20, paragraph 2, "only one carrion allowed per passenger."

a. so the character can express his thoughts
b. so the audience will learn the vulture's name
c. so the reader can tell what the stage looks like
d. so the actor can step out of character