For myself, I was getting a lot of alerts for shadows from trees when the wind blows, clouds passing in front of sun, etc. Using Deepstack I have eliminated about 90% of those alerts. If Deepstack doesn't see any of the objects you specify it cancels the alert.
You can avoid a lot of false alerts because you can pick what kind of object you want to track.
For example I get a lot of false alerts from shadows and tree movement. I have Blue Iris to only alert me when people are in a certain area..
Comes down to what you are wanting to do and your cameras field of view. For many people, the native motion detection or the motion detection of the camera are more than adequate for their needs.
For some cameras field of view, the motion detection is spotty and everything triggers it, so Deepstack can help cancel out a lot of the false triggers.
With 8 cameras, I am using DS on only 2. One uses it only during daytime because of shadows on a reflective driveway (which is probably 70% of the field of view), and on a separate camera only at night due to that one being particularly attractive to spiders and their webs.
I use it to reduce false triggers from shadows moving, as has been mentioned, and as a sort of alarm system to monitor human and vehicle activity all around the house/yard. I clone the cameras and set up detection for those specific areas I want to watch and at a very sensitive level then filter using DeepStack, Works quite well.