Why does English pronunciation differ from spelling?

Why is the English language not phonetic? Why so big a difference between orthography and pronunciation?
That is to say one pronounces differently than he writes in Roman Alphabet. Is he aware of it?
Why do English speakers pronounce any vowel (i e a o u etc) as any vowel sound plus schwa etc?
They do not know when you tell them a foreign name how to transliterate (in Roman/Latin).
For example when you tell them “ Pescara” they always ask you to spell it. They think it is spelt as “Puscure, Paskari, etc”. Confused of so many possibilities. They write “Lux” pr /luks/, but they pronounce /laks/. They write “xylophone” pr. /ksylofon/ but they pronounce /zailofoun/, victuals /viktuals/ but pronounce /vituls/ etc. (sorry I do not use phonetic symbols)
Is Education not responsible to teach them how to transliterate foreign words at least in Latin?