It could be age. I've never been a sleeper, and some of my friends told me that'd change once I turned 40. Didn't. I'm still going to bed about 1:00 am and getting up at 6:00 on workdays /8:30 on weekends. But many of my friends say they need more sleep than they did when they were younger.
One exception to the above:
Could you have a medical issue? I won't go into details, but for a period of about a year around 45 I found myself exhausted all the time. I mean, I was going to bed early at night, still was dragging myself out of bed in the mornings, exhausted all day at work, no energy when I came home ... I wondered if my friends (mentioned above) had been right, and my personal timeclock was a little later than theirs ... it came on slowly, and after about a year of this, I said, "NO MORE. Something is wrong; this isn't normal." I went to my regular doctor (whom I usually like very well), and he was a bit general and dismissive: aging, need more exercise so you'll sleep more soundly, improve your diet ... no, no, that wasn't it. I went to my OB/GYN for a regular appointment (ladies, those yearly appointments are important), and she figured it out right away: It was a girl-y problem, and she fixed it with surgery. As soon as I was healed from the surgery, I was myself again. Plenty of energy, back to my old sleep schedule. I'm embarassed that I allowed it to go on a whole year. I blame it on two things: The problem came on slowly; if it had started literally overnight, I'd have been quicker to go for professional help. Second, my brain was muddled from exhaustion.