Why are the Latin and Greek alphabets the only ones with capital/minuscule letters?

There are a few others, but they are mostly neighbours of Greek and Latin, or else motivated by them.

Letter case – Wikipedia

Writing systems using two separate cases are bicameral scripts. Languages that use the Latin, Cyrillic, Greek, Coptic, Armenian, Adlam, Varang Kshiti, Cherokee, and Osage scripts use letter cases in their written form as an aid to clarity. Other bicameral scripts, which are not used for any modern languages, are Old Hungarian, Glagolitic, and Deseret. The Georgian alphabet has several variants, and there were attempts to use them as different cases, but the modern written Georgian language does not distinguish case.

Now, of these, Cherokee, Osage, Deseret, Adlam, Varang Kshiti are recent scripts, that got the idea from Latin. That leaves us with:

  • Cyrillic, whose lowercase is pretty half-hearted—they look just like the uppercase, and they’d have gotten the idea from Greek and/or Latin (Peter the Great) anyway.
  • Coptic, Armenian, Georgian, Glagolitic, which are also immediate neighbours of Greek.
    • Georgian used to be cased, and now isn’t. The uppercase and lowercase look different. (Meaning, they look authentic, originating in cursive.) EDIT: I was wrong: Georgian scripts – Wikipedia . The introduction of case, by mixing two historical variants of the script, was a shortlived innovation in the 1950s; historically Georgian was never cased.
    • Armenian lowercase also looks different.
    • Not sure how much case was used in Glagolitic.
    • Coptic is now cased, but my impression from Googling is that casing is rare; Bicameral scripts speaks of “limited modern use”, and any facsimiles I’ve seen of Coptic were unicameral.
  • Old Hungarian: if you read the fine print in Old Hungarian alphabet, not really cased, just makes the first letter of proper names slightly bigger. And Old Hungarian would presumably have gotten the idea from Greek or Latin as well.

So all the scripts that have case are either modern, and got the idea from Latin, or were neighbours of Greek. They developed case either at the same time as Greek and Latin (9th century), or later on.

The explanation is that case was a meme that originated in Latin and Greek, at the same time—independently or not, who can tell; it originated as a space compression technique associated with the high cost of parchment; and it spread out geographically from Greek to its cultural neighbours. It didn’t spread any further than Armenian and Coptic. Arabic and Syriac would have been next, and I don’t think their letter shapes would have made sense with case. Amharic would have made more sense I guess, but I don’t know how much cultural contact there was between Coptic and Amharic, and I don’t think casing was that prevalent in Coptic anyway.

What are some languages/dialects whose speakers call male bus drivers “master”?

Russian: Addressing taxi/bus driver by “шеф”/”командир” – where does it come from?

A taxi, and particularly a bus driver, is the “chief” or “commander” of a small mobile unit with a lot of “horsepower.”

Such a driver is also responsible for the safety of several passengers. At least in New York City, this person is “in charge” not only of the vehicle, but everyone that is in/on it at any given time. A bus driver has the right to ask a passenger to move (to balance the vehicle) give a seat to a handicapped person, or do other things that make vehicle safer. Assaulting one carries extra penalties otherwise associated with assaulting a policemen.

Any Russian speaker in the city would understand why such terms are used.

In fact, Russian is a far better illustration of “master” for bus drivers than Cypriot Greek, which the question details suggest.

The Cypriot Greek term alluded to in details is mastros, which is cognate with master in English, and which derives either from Old French maistre or Venetian mestre. It has a cognate in Standard Greek mastoras, which grammatically points back to Byzantine Greek maistor, and ultimately Latin magister. (Of course, magister is also behind maistre and mestre and master.)

The thing is, words related to master don’t just mean “master”. Some of you will have noticed me address Michael Masiello as Magister, for example. That’s the (Mediaeval) Latin for “teacher”. A teacher is a master of their pupils, particularly in the old school way of schooling.

In Cypriot, the primary meaning of mastros is “boss”. A boss is a kind of master, but it’s the kind of master that makes sense under contemporary capitalism, rather than mediaeval feudalism.

There is a secondary meaning in Cypriot of mastros, which corresponds to the primary Greek meaning of mastoras. That meaning is “craftsperson, tradesperson”, and by extension “expert”. And it’s the friendly term with which you address a builder, a plumber, a carpenter, and so forth. It acknowledges their exercise of a practical skill.

That sense of course is hardly alien to English: we have master craftsmen and apprentices, we speak of someone being a master of their art or craft.

I don’t know for a fact why a bus driver in Cyprus is addressed as mastros. It could be, as in Russia, that you address him as “boss” because the vehicle, and your life, is entrusted in his hands. My own hunch is that you address him as “craftsman”, like you would any builder or plumber, out of deference to his professional exercise of skill.