As in many other languages, phonetic changes have occured in Japanese over the centuries. One of them is with "wi". We actually used to pronounce the mora "wi" as "wi". The hiragana for that was 「ゐ」 and the katakana, 「ヰ」.
In our time, however, this syllable has disappeared and has been replaced by the consonant-less 「うぃ」 and 「ウィ」, respectively. Thus, 「ウィル・スミス」 is currently the only "proper" way to pronounce "Will Smith" in Japanese.
In English, you no longer pronounce the letters "g" and "h" in the word "daughter", do you? I won't even mention "knight" as you only pronounce half of the letters in it. So what we are discussing is not a phenomenon unique to Japanese.
"Whisky" in Japanese is 「ウィスキー」. Just as in 「ウィル」, it starts with the vowel 「ウ」 and not the consonant "w".
「ゐ」 and 「ヰ」, which I mentioned above, are now used only for aesthetic purposes. Use them daily and you simply will look very weird. Take a look at the official website for Nikka Whisky:
It says 「ニッカウヰスキー」. That does not mean, however, we read it as "Wiスキー". The "wi" syllable is long gone in sound if not in kana/spelling.
Listen to the very first syllable in this commercial.