For scheduling, not for viewing (sheesh)
I thought exactly the same thing and contacted Apple Support to get the skinny.
They say the pref "Day Starts..." etc. is for allowing people to request meetings within a period of time (your day), not for viewing. I suggested this was not expected behavior.
The support guy admitted that this was both unclear in the preferences and probably insufficient. He said he would submit a request for a) better clarification within the preference pane and in related support docs and b) put in a suggestion that many people would like to have a default view that corresponds to the "day" as specified.
I suggested a simple toggle switch that says "also set this as my default Day view" would not add a big burden to the preference screen.
Don't know if this is the correct part of the forum, but icloud calendar is driving me nuts. My working day starts at 7am and finishes at 8pm (for the purposes of viewing my calendar). However icloud shows the day from Midnight to 23:59 which means that I can only ever see part of my calendar. In Ical you could change the length of your day - anyone any idea whether you can do this is Calendar? Thanks in advance!