[HeinzStuckeIt]

> Same with place names that you've never seen (the name of some random village you see on a map)

I’m just guessing here, albeit as someone with linguistic training: toponyms in a given region are typically formed by a limited inventory of words (“topoformants”) possibly extended by, for example, the name of a landowner, a tribe, etc. (a “specific”). Speakers growing up in a region will subconsciously learn the typical topoformants and therefore be able to read at least them without the vowel markings.

Also, don’t forget that Arabic does write the long vowels through the use of matres lectionis. It’s the very early Semitic inscriptions, from before this device was invented, that I am amazed that anyone could read.

[Sam6late]

In some occasion, when I was a student as native speakers, we came across people who would say words that would be hilarious to hear. They would drop a hidden vowel and say some words that made us laugh because they would allow two consonants clusters which is not used in Arabic. Such as Kamouj al bahr,instead of Kamouji elbahr (as sea wave).'The principle that two vowelless consonants (saakin letters) cannot meet is a fundamental rule in Arabic pronunciation, often referred to as التقاء الساكنين the meeting of two saakin letters).This is why English spoken by some Arabs, Egyptian in particular, has a distinctive accent that reflect that, so James sounds Jamsi, Street becomes Istreet.