Anyone can call CPS as many times as they want and they will investigate, but no one is putting kids in foster care for biking to the store unless there are other things going on.
Are you saying this from personal experience? Because it sounds like you’re spreading an urban legend. Parents aren’t being investigated for kids biking around. CPS is way too busy for that.
I have relatives who work for CPS and if anything they are extremely lenient. And even if they take kids (when both parents can’t take care of the kid for example if they’re both heroin addicts) CPS will try to place with a relative, even out of state.