Some other items worth considering in the context of why mortality rates look the way they do:

https://doi.org/10.1006/jtbi.2001.2430

"Reliability theory is a general theory about systems failure. It allows researchers to predict the age-related failure kinetics for a system of given architecture (reliability structure) and given reliability of its components. Reliability theory predicts that even those systems that are entirely composed of non-aging elements (with a constant failure rate) will nevertheless deteriorate (fail more often) with age, if these systems are redundant in irreplaceable elements. Aging, therefore, is a direct consequence of systems redundancy. The theory explains why mortality rates increase exponentially with age (the Gompertz law) in many species, by taking into account the initial flaws (defects) in newly formed systems."

https://doi.org/10.1073/pnas.1714478115

"For many cancer types, incidence rises rapidly with age as an apparent power law, supporting the idea that cancer is caused by a gradual accumulation of genetic mutations. Similarly, the incidence of many infectious diseases strongly increases with age. Here, combining data from immunology and epidemiology, we show that many of these dramatic age-related increases in incidence can be modeled based on immune system decline, rather than mutation accumulation. In humans, the thymus atrophies from infancy, resulting in an exponential decline in T cell production with a half-life of ∼16 years, which we use as the basis for a minimal mathematical model of disease incidence. Our model outperforms the power law model with the same number of fitting parameters in describing cancer incidence data across a wide spectrum of different cancers, and provides excellent fits to infectious disease data. This framework provides mechanistic insight into cancer emergence, suggesting that age-related decline in T cell output is a major risk factor."

And of course the SENS synthesis of the compelling evidence for aging to be the consequence of accumulated damage of various sorts:

http://www.sens.org/research/introduction-to-sens-research

"Many things go wrong with aging bodies, but at the root of them all is the burden of decades of unrepaired damage to the cellular and molecular structures that make up the functional units of our tissues. As each essential microscopic structure fails, tissue function becomes progressively compromised – imperceptibly at first, but ending in the slide into the diseases and disabilities of aging. Decades of research in aging people and experimental animals has established that there are no more than seven major classes of such cellular and molecular damage, shown in the table below. We can be confident that this list is complete, first and foremost because of the fact that scientists have not discovered any new kinds of aging damage in nearly a generation of research, despite the increasing number of centers and scientists dedicated to studying the matter, and the use of increasingly powerful tools to examine the aging body. In its own way, each of these kinds of damage make our bodies frail, and contribute to the rising frailty and ill-health that appears in our sixth decade of life and accelerates thereafter."