Most people don't realize that no bird naturally lays one egg every single day, as most modern laying hens do. Daily egg-laying is a result of genetic selection and is extremely bad for a hen's health.
Because there is a positive correlation between the number of eggs laid and the incidence of ovarian cancer, every egg a hen lays brings her one step closer to death. Modern laying hens are so prone to reproductive disease that they have been studied extensively as a model for human ovarian cancer -- and the negative impact off excessive laying on a hen's health is extensively documented.
For the egg industry, reproductive disease is not a concern, as they kill hens at the young age of 18 months and ship in a new batch. For backyard chicken keepers, the physiology of modern layers becomes problematic when people find they do not want to care for an animal who is past her prime after only two years, yet can go on to live another decade and require thousands of dollars in veterinary care to stay healthy and alive.