a helmet and ballistic shield would be more practical to have on standby for home defense or protection in incidents of civil unrest like rioting or looting
This is a cogent point.
Human body has a number of vulnerable points--neck, armpits, front half of the pelvis, and both thighs. All of these areas are hard to protect. Which gets more complicated when you do not have certainty on the threat axis.
Now note this shows both the benefit and the liability of a good shield. Shield gives a big arc of protection, but, only if the threat is in that arc.
On helmets, a person will read and hear much on how the head is a small, moving, target, and hard to hit. And, it is. Except for when it's not--like if you are focused on something, or aiming, or using binoculars or the like. The head is somewhat
more vulnerable to smaller, and lesser, injuries than the rest of the corpus vivendi. This is one of the reasons that militaries all adopted helmets about a century ago. They didn't have to be perfect, just good enough (80% of battlefield casualties are from low velocity, <300 fps, fragments). But, helmets restrict sensory inputs, too (many of which are concentrated in the head).
You also need practice wearing one, too--you need to build up neck strength becasue your head has a different mass and inertia with a helmet than without.
Helmets have become pretty standard for a number of thing nowadays, too. Climbing, biking, even the ubiquitous hard hat. Each can offer some protection. The question becomes how much protection is "enough."
And, that latter is the conundrum. There is no simple answer for how much is enough. I can't answer that question. Not even, universally for myself. If I lived in a higher threat environment (I don't, as part of a layered strategy) I would look harder at some of the shield that are out there. I'd probably take the weight penalty and have a vision port, too (f there's enough threat for a shield, there's more threat than worth poking a head around to eyeball what's going on).