G'day Dazbo,

"Why is the top string (vertically speaking) tuned to a higher pitch than the two below it?"

That's a "re-entrant" tuning ... if you think of the standard "C" chord on a 'C'-tuned Ukulele (dGBe) the chord (due to the octave higher string) is sounded eGce ... so the 'e' at each end is the same note. This means that quick up-&-down strumming techniques sound more 'even' as they don't particularly run Up then Down ... only the middle notes show a different order.

This type of tuning is used on a lot of South American stringed instruments - for the same reason. The way we are accustomed to tune a 6-string guitar ... for our particular style of music does not create an absolute rule. Enjoy the Ukulele for what it is and what it does ... not what some preconception says it should do.

Regards,

Bob