The only reason to turn that button off I have found (in other vehicles) , is if you are ever backing up with a towl vehicle attached, or sometimes snow gets crammed in the sensors, and the system will beep annoyingly until the snow is cleared out.
Aside from those 2 instances, or a malfunction with the sensors, I would leave it on all the time..... I'm not sure why that button got such an up front and center spot on the Envision dashboard - for button it doesn't get used, in reality, very much.
2017 Envision Premium I AWD 2.0T (Summit White)
2014 Impala LTZ 3.6 V6 Limited (Summit White)
2010 Lincoln MKS AWD Twin Turbo; Livernois Motorsports tuned; 0-60 3.94 seconds (Steel Blue Metallic)