Things I notice about routes

I have been looking at flight aware online and notice some things. Any comments would be appreciated.

1. Some airlines are strong during the day but lose numbers at night. Some airlines are consistent throughout the day and night.

2. The last east to west flight leaves much later than west to east flights..

3. Very few flights, if at all, from west to east, arrive between 1 and 4 am. If there is a west to east flight, typical is for it to leave the west coast at 11 pm and arrive at 5 am, almost always coast to coast. I don't see any SFO to DEN flights that arrive at 3 am.