It is using the Romance (i.e the original Latin) vowels. English got its vowels all garbled and messed up by the great Vowel Shift, so now every Latin vowel in English does not sound how it is supposed to sound. Heck they don't even follow the same rules most of the time, because English spelling is fucked up beyond repair. That's ironic because that makes writing English much more complicated, even though the language is quite simple to learn at a basic level.

A is /ei/ and lots of other sounds.

E is /i/, sometimes it's an open e, ..

I is /ai/, sometimes not, ...

O is always a diphthong, plain /o/ does not exist anymore

U is /a/, /ju/, ??

Y is there for the show, often it's used for /j/

English like German has lots and lots of vowels, while Latin and Italian have like, 7? The letters were supposed to have only one sound at most, but history clearly shows us that it's easier to reuse or adapt an existing letter than invent a new one (look at [ng] for instance, or [th] which became used mostly because nobody had types to print thorn and eth).