Because there is no ł in English orthography – Polish złoty is refereed to as either "Zloty" or by its international abbreviation PLN in English.
well that's probably because most people can't type the ł, which doesn't make "zloty" correct
if you look at other wikipedia articles that have Polish names in them (or any other language with accents), the accents are kept in most of the cases (except when an English name exists, like Warsaw instead of Warszawa, and Silesia instead of Śląsk)
Personal names are something that rarely changes from language to language unless the alphabets are different. They often appear in documents, after all, so uniformity is expected. Same with toponyms. Currencies, though - not so much. Their names may change in accordance with the language, and in official documents they can be referred to by acronyms like USD, EUR or RUR, to avoid any confusion.
In the UK at least loanwords do often keep their accent but are commonly written without, unless the person wants to appear slightly fancy. eg. on signs or a menu you will often see café while almost everyone in common conversation would use cafe.
It's not wrong to use 'złoty', but many people will have difficulties pronouncing it, and if they don't have a keyboard with the 'ł' glyoh installed, they'll have trouble typing it.
Similarly, the country of Curaçao is spelled with the 'ç' or with a 'c'.
I always use zloty in English even though I always leave my settings on my keyboard as Polish. Strangely, Wikipedia writes it as "złoty" on the English page.
I've been studying polish for months, and only now am I learning what a złoty is...
Since I learned the Polish word, I always say and write złotych (or złoty etc. obviously where appropriate), even when the rest of the sentence is in English. It's the Polish name for a Polish thing that we don't have in amy English-speaking area, so why should we anglicise the name for it or have our own name for it? I mean, yeah ok, maybe accept it without the stroke through the l and undeclined in an English sentence if some people don't have the diacritics on their keyboard or feel weird declining nouns when writing in English, but if I write złotych there's no way that's wrong, is it?
That's a good question. As 'ł' in the default English sentence is concerned, I guess maybe there's no need to wait for the new course to change it - I changed it at least in those three sentences in this section.
As for "złotych" in the English version... on one hand, Wikipedia states that "The recognized English form of the word is zloty, plural zloty or zlotys." On the other, it uses the "złotych" form 48 times anyway. So... I guess it should be accepted. Added now.