In chapter 1:14, Mr. Collins provides a list of three reasons for marrying Elizabeth.
Mr. Collins does not list the reasons in the most romantic way, and they are not the most romantic reasons.
Reason 1: A clergyman should be married. This sets an example for the men in the parish to marry.
“I think it a right thing for every clergyman in easy circumstances (like myself) to set the example of matrimony in his parish” (63).
Marriage is an honorable endeavor, of course. Since Mr. Collins wants to be a role model for the parish, he thinks he should be married. For him not to be married would be strange or improper.
Reason 2: Marriage will make him happier.
Mr. Collins seems to think that marriage is a good idea because he is “convinced that it will add very greatly” to his happiness (p. 63). Notice that he gives this reason second, almost like it is an afterthought. He might be happier if married, but it is not his first motivation.
Reason 3: He was told he had to marry.
Apparently Lady Catherine, the noble woman, he calls his “patroness” reminded him that he needed to get married quickly.
A clergyman like you must marry. Choose properly, choose a gentlewoman, for my sake and for your own; let her be an active, useful sort of person, not brought up high, but able to make a small income go a good way. (p. 63-64)
I suppose this is the closest thing to a compliment he said. It does make Elizabeth seem like quite a catch! He is at least implying that she is a good wife. What woman wouldn’t want to be called useful!
Due to the way property was passed down, when Mr. Bennet died the land would go to his cousin.
Mr. Collins ... when I am dead, may turn you all out of this house as soon as he pleases (ch 8, p. 39).
Sadly, this is enough reason for the family to encourage Elizabeth to marry Mr. Collins to keep the land in the family. It also depersonalizes the decision, at least as far as they are concerned. He really must marry one of the Bennet girls. It puts all of them in an extremely difficult position.