Students have skills that are applicable to Canadian society such as all their professional knowledges are in English, and all skills (like engineering, nursing, etc) are situated in Canadian environment and highly probable to contribute better than FSW outlanders. Before they were even evaluated lower than FSW cuz it is merely impossible to get a PR for a student without PNP or LMIA. Now it is just fair.
On the other hand, people with siblings do not necessarily have the skills Canada needs. They might settle faster, but what can they do? Does having a sibling define what kinda skills you have to contribute after you settle down? Canada does not want people who can just settle down but sit home all day.