It is advantageous to have relatively few timezones rather than everyone using hyperlocal time. If you accept that then consider that most timezones are biased towards the point where noon is at 1200 being in the east of the region, leaving the western side with their daylight hours particularly biased towards the early morning. In some sense an adjustment to +1 merely moves the bias so that most of the region has physical noon after 1200 instead of before it, and this tends to strike a better balance because early in the morning is not considered a particularly sociable hour.