The failure of many systems at approximately the same time is selected for. Death as a result of the failure of those many systems is not itself selected for, but the reproductive benefits of systems that only have to function for a set amount of time are selected for. It's not exactly correct, but it's a reasonable approximation for talking to laypeople, as it's close enough to the truth to allow people to make reasonably accurate predictions about the world (e.g. this new wonder drug won't cure aging). Whereas if you say that aging is "accidentally linked" to another trait, that makes it sound like we just have to identify one or two traits and we can cure aging, so while it may be closer to being literally true, it's also more likely to cause misconceptions in people who don't have more than a layperson's grasp on the mechanisms of evolution.