The simple fact is that no time is perfect for everyone. Our contractors select times that work for them: we occasionally make suggestions, but we don't dictate chat session times. Most of our contractors are teaching classes around other jobs. Also, if we restrict ourselves to sessions that begin after 7am on the Pacific Coast and end by 5pm on the Eastern Coast, we would have to overlap many more courses, and reduce student options. By spreading out our teaching "day", we are able to contract with good teachers who otherwise would not be able to teach for us, and allow students more flexibility in assembling a curriculum with several courses.
Not all students handle early (or late) hours the same way, so you need to consider how well your student can perform at these times. We have taught taught math, science, language and literature courses at both ends of the day for ten years, with attentive — and even enthusiastic — participation by many students, including some who were living in Hawaii and Alaska, as well as outside the US time zones entirely, in India, Jordan, Mozambique, and Spain.