I"ve always felt that being left-handed would make learning a normally set-up guitar easier (a guess, as I'm right-handed.) After all, the left hand requires more strength and, unless you're going in for really fancy finger picking, more dexterity.

Am I wrong?

Somewhat. If it's such a good thing, why aren't 90+% of guitars made left-handed, so righties can take advantage of it?

It's generally true for beginners that the most challenging thing is the fretting, normally done by the non-dominant hand. But my understanding is that as one advances, the requirements for the picking (dominant) hand can be even more demanding, hence the traditional design and use of guitars.

Another factor is position. For most people, holding a guitar the "other way round" feels quite awkward. It's natural to want your dominant hand in close and your other hand reaching out (think holding a rifle, boxing, etc.). Many lefties find this less of a concern than finding and sharing instruments, and choose to play right-handed -- but bear in mind that in many areas, finding a good lefty guitar is a MAJOR challenge. Hardly any righties seek out left-handed guitars.