If you're saying "your distribution can't automatically update you if libc is vulnerable to something", that's true. More CPU time is required to react to major vulnerabilities, as everything has to be recompiled. However, it's not much CPU time, and the downsides of requiring more compute time are lower than the upsides of knowing exactly where your dependencies come from. And having your "getting started" instructions be "1) install bazel 2) bazel run //your:binary".
My point here is to be able to install a new package when it's out, without disrupting the whole environment. For FreeBSD, for example, the new Firefox is already available. I have installed it, and it wouldn't run. I had to auto-update 300 MB of other stuff, including LibreOffice, PyCharm and even TeXLive, to get the system up to date for the new Firefox to be able to run.