Prop guards, Training wheels for your drone

Good for some flights, indoors, low in forest under tree canopy in case of tree trunk bumps, other such close proximity situations.
They really are useless for dramatically lowered human impact safety.
Yes, they will affect flight times, they will add flight stress to windy situations, quiet often they can increase risk of loss of an aircraft rather than offer desired protections some feel they give.
Used in the right circumstances they can be a good precaution and helpful.
Most pilots flights you see they are pointless and cumbersome.