Magewights are actually not that rare. If you looked hard enough, you could probably find a few, and the minimum to make use of of a single level is simply an intelligence of 12, which is easily achievable with a non-elite array. Magewights are
1% of the population, and they're much less likely to die because they're valued for their skills outside of combat, not just using wands in it.
Wizards and
Sorcerors, now those are rare, the equivilant of our professional engineers, doctors, and bigwig scientists.
And Magic Missile is the least practical spell ever to stick into an Eternal Wand. If you want to consider 1'st level spells, things like
Obscuring Mist,
Mount,
Silent Image, and
Enlarge Person are all far superior in terms of bringing useful magic to the battlefield at 1'st caster level.
At second level, things get much more interesting. Area of effect crowd control becomes available, such as
Glitterdust,
Web,
Summon Swarm, and
Hypnotic Pattern. Actual battle magic is passable with things like the infamous
Scorching Ray shotgun,
Blindness/Deafness,
Acid Arrow, and
Flaming Sphere. The infamous utility of
Invisibility and
Rope Trick. Highly practical spells like
Whispering Wind,
Darkness,
Darkvision,
Pyrotechnics, and
Protection from Arrows.
And, of course, rocket-launcher good at level 3 spells. The ever popular
Eternal Wand of Fireball, which lets to roast most ordinary mortals at 600 feet, or dent more seasoned troops, twice a day, refills once every day, without fail.
Haste, which shows that superspeed is indeed good on a battlefield.
Wind Wall, shielding your siege engines from Alchemist's Fire and Flaming Arrows in a tight corner, reliably in nearly all situations.
Stinking Cloud, making those opposing mages throw up and regret eating breakfast that morning.
Clairaudience, giving people satalite imaging before satalites were imagined. And so on and so forth.
Really, there are a ton of reasons why they invented the Eternal Wand instead of guns. Maybe it's the endless versatility of magic that can be imprinted on a single blueprint item, rather than highly inaccurate bits of lead that need to be fired in huge volleys to be
any good, and have a good chance of blowing up in your face? It took decades of experimentation, refinement, and face-slapping to get anywhere near the guns we know and love oh-so-dearly. Why build suicide machines tomorrow, when you can build rocket launchers that recharge infinitely,
now? Not to mention that you can use the same blueprint for a rocket launcher, make a few changes, and have long-range scouting capacities.