Alfred Doolittle has had a long history as a ne'er-do-well when he becomes the beneficiary of Ezra D. Wannafeller, an American philanthropist, and suddenly finds himself receiving four thousand pounds a year in income. This catapults him into the very well-to-do middle class. This means he is pressured to adopt middle-class morality. He finds this morality confining and annoying.
For example, he is now expected to marry the mother of his children in order to be accepted as respectable, whereas when he was poor, nobody cared whether he was married or not. He is annoyed too because now his relatives, who had before ignored him, have come clamoring around wanting his acquaintance in the hopes he will give them or leave them money. Further, doctors are now finding all sorts of things wrong with him for which he needs costly medical treatments, whereas before they hadn't had the least interest in his health. He finds middle-class expectations that he behave in a certain "upright" and responsible ways, such as by marrying, acknowledging his relatives, and taking care of his health, a burden and a bother.