A semi-common debate is whether or not one should attach a sling to one's home defense shotgun or rifle.
You might need hands free to transition to a handgun, manipulate a flashlight or light switches on the wall, open or close doors, deal with children or other family members, or operate a phone or alarm panel.
If someone manages to grapple with you while you're slung it will make it harder for them to get the gun away from you, and you'll be able to use your hands to some degree to fight.
The sling has the potential of snagging on things, and it takes some small amount of time to sling the weapon on your body.
Some would say it's not needed since home defense engagements tend to be short and you would want the gun in your hands the whole time anyways.
Adds cost, since you need to buy a sling and potentially mounting hardware. This wouldn't apply if you would have bought a sling anyways for field / class use, just not for home defense.
Most slings will prevent you from easily transitioning the gun to your support side, e.g. if you wanted to go around a corner to the left.
Having a sling on a long gun for home defense is worthwhile. A well adjusted sling should not snag on anything and should be very quick to put on your body. The ability to use your hands without putting the gun may be tactically valuable for a number of reasons. A sling on a long gun is equivalent to a holster for a handgun, except it's even more convenient because it stays attached to the gun.