Remember, Katherine Howard was not even 20 when she was executed, and ignorant and rather stupid, and had no mother to get her off or see her otherwise married, and that Dereham loved her, and wanted to marry her.
Elizabeth's own mother had had her head cut off by her father. She likely equated marriage with death, and childbirth with such.
Women were nothing but chattel to men, even queens.
Parliament combined wanted a male in power, so Elizabeth never named her sucessor, only made a sign and ascented when she was past the power of speech that it was to be James, the last man standing, a Protestant king already married to a Protestant princess and the father of, at the time, two living sons.
Until very recently and in many ways now a woman is subject to a male and so when we watch this show it is entertainment but to any woman then it was real life.
When Robert Dudley himself died he praised his wife, Lettice Knowles, for being obedient.
If you have the chance read Ackkroyd's bio of Sir Thomas More and gain insight into his ideas of feminine equality and his pursuit of this as much as he could within the time in which he lived and its constructs. He did the best he could for a 16th century man.