Most Germans don't even know the rule governing whether to write "ß" or "ss" anyway.
That was quite normal with the "old" orthography, where the rule was very complicated,
but the reform of 1996 made it very easy:
- long vowel or diphthong = ß
- short vowel = ss
So you write Preußen (diphthong, i.e. double vowel in one syllable), Straße (long a) and Klasse (short a).
(The only exception is when writing in capital letters, because there is no capital ß: Straße, but STRASSE.)
One advantage of the new rule is for people learning German:
the way the word is written reveals how it is spoken.
Except, of course, if it has been written by an ignorant
