That brings it down to the fact that the Lusitania was smaller and didn't have room for as many passengers. And the segregation between the first class passengers like Vanderbilt and the passengers in steerage below the decks was total and complete. They didn't even see each other. Now the only segregation is for meals in the Britannia Dining Room or the Queen's and Princess Grills. Some of the dining venues are common to both: the King's Court and Todd English.
The differences in the two Cunard ships --- with almost one hundred years in between -- reflects the changes in society during that century.