Why is »ß« substituted with »ss« rather than »sz«? Why SZ could (or have been) be used instead of SS The traditional orthography encouraged the use of SZ in place of ß in words with all letters capitalized where a usual SS would produce an ambiguous result One possible ambiguity was between IN MASZEN (in limited amounts; Maß, “measure”) and IN MASSEN (in massive amounts; Masse, “mass”)
Use of ss or ß in a surname - German Language Stack Exchange People with an ß in their name who emigrated from a German speaking country to an English speaking country changed their name in the manner that the ß either became sz or ss (sz was the old transcription for ß), and so there might have been an ancestor of you who had the name »Voß« but when he moves to another country he changed his name
blackletter - What is the linguistic necessity for the letter ß in . . . A double consonant, such as ss, marking a short vowel is characteristic for the German spelling system Marking the distinction between [s] and [z] is unnecessary in other contexts: Initially, there is only <s>, pronounced [z]; and in final position, there is only [s], written as <s>, <ss> or <ß>, depending on what happens when a vowel is added: Gras - Gräser long vowel + [z], Fuß - Füße