SageRod,
A lot of folks do carry almost 24/7. And many more carry a weapon part-time, legally, in states that permit CCW.
You asked why not just slip it into your waistband without a holster. I can give you 3 good reasons for that if you're male. Some guns with no external safeties, such as the Glock, may snag the trigger while "tucking in". If that happens, you run the risk of going around half-cocked (which is not referring to your gun) or not having children.
A good holster will --
- Provide security for the handgun.
- Protect the handgun's mechanism and potentially it's finish.
- Keep the gun in the same location at all times
- Present the grip of the gun at a constant angle for drawing
- Provide some protection from accidental discharges
Using a properly fitting holster keeps your gun on your person even if you are running, traversing stairs and even when tussling on the ground with an assailant. It can also secure your gun against someone trying to grab your gun in a close physical encounter.
Holsters also protect your gun against your body. Body oils and salts from perspiration can cause corrosion quickly on many guns, even stainless steel guns if neglected. Holsters can reduce the amount of exposure.
With a gun tucked into a waistband, there are some motions that can cause a tension change at the belt-line. Reaching up high (in a market) may allow your pants to ride down or your gun to "slip" deeper inside, possibly down your leg. Squatting down several times might cause the muzzle to be pushed up until the gun's balance allows it to "fall over" the belt onto the ground.
Even if your waistband carry is tight enough, the gun can still move around, such as lowering the butt closer to the belt line where it's difficult to grab. A holster allows the same reach & grip each time, increasing the speed of your draw if or when needed.
A proper holster covers the triggerguard in a way that reduces chances of the trigger being activated or getting snagged. Some holsters also feature either a tension-screw to help secure the gun or a "thumb-break" safety strap over the rear of the gun or between a semi-auto pistol's cocked hammer and the firing pin. These also help with #1 - securing your weapon.
Some guns may discharge when dropped and it's prudent to expect that ANY gun might fire if dropped from waist height to a solid (concrete) surface.
If you want to know the value of a holster, try doing about 30 jumping-jacks with your
unloaded XD carried without a holster.