They absolutely are improving their own classifiers by getting customers to use their classifiers, so yes, they benefit from us using their services. I guess it depends on what it is you are uploading, in my case, I do not mind if Fungibot contributes to a broader level of fungus identification and understanding - this type of knowledge is a good thing in my opinion. I can see however that there would be cases where this would not be a good thing and an invasion of privacy.
I have copied this snippet from the Microsoft privacy site: "Microsoft Cognitive Services help developers build apps that can better comprehend data, such as by detecting faces and objects in images, understanding spoken words or interpreting commands. We collect and use your data to provide the services, which includes improving and personalising your experiences.
Cognitive Services collect and use many types of data, such as images, audio files, video files or text, all of which are retained by Microsoft. Microsoft has implemented business and technical measures designed to help de-identify some data that Cognitive Services retain. De-identification will not anonymise data completely; for example, a person in a photograph could still be recognised by someone who knows that person."