Are we all talking about the orange "hey - there's a vehicle beside you!" indicators near each rearview mirror?
I can understand why those are disabled below 20 MPH as the BLIS might tend to blink annoyingly in a drive-through or pulling into your garage.
The front and rear parking sensors and cross traffic traffic alert on the other hand work only at slow speeds. You don't need BLIS in a parking lot, but you do need parking sensors and cross traffic alert.
Just making sure we're all on the same page here since some people tend to confuse the blind spot information system with parking sensors or cross traffic alert.