Why do Y and Z end the alphabet?

The Romans adapted Greek to form their own (Latin) alphabet.

Initially they did not include Y or Z, believing them to be unnecessary. Later, however they began incorporating more Greek words into Latin vocabulary. At this stage they added Y & Z - at the end of the alphabet.

What are the most used letters in the English alphabet?
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Mark Forsyth (The Inky Fool) has analysed Google Search query result data for lines of verse requested online. Here is the Top Ten:

58 countries list English as an official language - but not the UK. The world's lingua franca or second language is not, technically, the 'official' language of its birthplace. The de factoofficial language of the United Kingdom is English,[3][4] which is spoken by approximately 59.8 million residents, or 98% of the population, over the age of three.[1][2][10][11][12] An estimated 700,000 people speak Welsh in the UK,[13] an official language in Wales

About the English Language