Allowing nature to run its course through some people being run over because they're too lazy to look both ways instead of just listening for vehicles is most definitely not the same as culling them. A cull is a targeted killing of many things at once (for example - goats and pest control).
While these guidelines will probably save some people too lazy to look both ways (a bit of a strawman for this argument), I suspect that the real reason is to protect people who don't have the capability to look both ways easily. People with vision disabilities come to mind first. Electric cars can come upon bicyclists quietly as well. And frankly sometimes you're just having a crappy day, distracted by some @#$% at work, and paying less attention. That happens to *everyone* on the planet. A little extra help from a noisy electric car can go a long way.