The Romans adapted Greek to form their own (Latin) alphabet.
Initially they thought Y and Z unnecessary.
Initially they thought Y and Z unnecessary.
Later they began incorporating more Greek words into Latin vocabulary. At this stage they added Y & Z - at the end of the alphabet.
English does not follow the convention of some Latinate languages where the letter is directly linked to the letter's origin (transcribed upsilon) in the Greek alphabet. The equivalent in Spanish is griega and i grec in French etc