Among European languages, English is maybe the language with the less consistency, when it comes to writing, but it is far from being the only one. French is another one, and English borrowed not only a lot of French words, but a lot of them were borrowed with their old French spelling.
To understand why English and many other European languages have such weird spelling rules, you have to start with the initial reason: religion. Most Western European countries used to be Catholics, and the main language of the Church was Latin. The Latin alphabet was designed to write down... Latin. The Romans modified and adapted the Etruscan alphabet, which was borrowed from the Greek, who borrowed it from the Phoenicians , etc. to their own language. However, when European languages developed as national languages, they faced a real issue, which was to adapt the Latin alphabet, which was ubiquitous in Western Europe, to their own languages. If you compare the spelling system of Hindi to Latin, you immediately see the problem.
The Latin alphabet is very poor and is composed of only 26 letters. And many sounds in Germanic languages do not have their counterpart in Latin. People started to use combinations of letters to represent their own specific sounds, which were pretty unique to each country. For instance, you cannot read Dutch if you apply English rules to it.
In the case of English, the problem is even more complicated. For one, the official language of England up to the 15th century was French, which explained why 40% of a text in English is composed of French words. Second, when people started writing in English, there was no government body to enforce a common spelling. So, printer shops all over England came up with their own ways to spell out words, and the result is this hogwash of spelling that is English today.
The last problem, which is a problem that many international languages, such as Spanish, German, French and Portuguese are faced with, is that every decision to change the spelling of your language should be the result of international comities. And since, there are so many different accents today, it has become quite difficult to come up with a regular pronunciation, and hence, a regular spelling for any of these languages. I can tell you that as a Frenchman, speaking Parisian French, I would have a hard time convincing Belgian or Quebecers that my accent is the right one... :-)
Now, a language usually becomes an international language when the country who speak it reaches some kind of dominance, it has nothing to do with any qualities this language might have. In Europe, this was the case for Greek, Latin, then Italian, French, German and now English. Machine translation might change this situation, but I doubt it, since English is so much ingrained into science and technology now. And the US, and most English speaking countries, have little interests to see their language loosing their prominence. We French speakers went this route after the Second World War... So we know the drill... Economically, this is a real bonanza, you can attract the best students, the best researchers, the best journals etc... You can impose your movies, your literature and of course your values... Why do you think Paris was the capital of arts and literature during the XIXth century? Language... Now it is New York or London... Language again.