In chapter 5, what is ironic about the cottage owner's refusal to put thatched roofs on their homes?

The Great Gatsby shows how, in the world in which the characters resided, class lines were strict and could not be completely crossed.  The old-money East Eggers might party with the nouveau riche West Eggers, but they felt superior to the West Eggers and wouldn't do more than occasionally rub elbows with them.  Certainly, neither the East Egg residents nor the West Egg residents had much to do with the people who lived in the area of town where the Wilson's lived, beyond, that is, using them the way Tom used Myrtle.  The brewer who built Gatsby's house and wanted the area residents to put thatched roofs on their cottages wanted them to do that so he could feel like the Lord of the Manor with his own little village of peasantry to rule.  Their refusal shows that they might work for the rich, but they had enough pride to refuse to be ruled by them.  Similarly, Myrtle might allow Tom to use her, but she refused to be completely subservient to him as she proved when she kept repeating Daisy's name.