That's what a personal assistant is for, to always be there when the boss wants her to be. And to do what he demands. This man wanted to relieve the tension - the assistant was at hand, without hesitation and took advantage of her. According to her cries and sighs conclude - this is the work she likes!
The tourist wanted to be fucked in exchange for a favor. The cab driver didn't mind, so it was a very profitable barter.