Why does ボウル use a vowel kana rather than a long vowel mark?

Question

It seems like both ボウル and ボール are valid Japanese words. The general impression I get is that using long vowel marks ("ー") are the norm for words written in katakana.

In Why are long vowels represented differently in hiragana and katakana? , explanations of vowel kanas being used instead include words that have kanji, or breaking up the sound. Maybe I'm just ignorant of how "bowl" is pronounced in either British English or American English, but neither explanation seems plausible. Why is ボウル spelt using a vowel kana?

Neither the Japanese Wikipedia article on ボウル, the Japanese edition of Wiktionary, or the English edition have an explanation for this particular word.

Answer 1

「ボウル」("bowl") is still often written 「ボール」 as very few people (loanword pronunciation nazi types), actually pronounce the two differently. 「ボウル」 is pronounced 「ボール」 by the rest of the nation.

(I never even knew that a sound like 「オウ」 existed in this world until I started learning English in junior high school. I am sure you have heard Japanese-speakers pronounce "Oh, no!" as 「オーノー」.)

One major reason that some prefer the spelling 「ボウル」 would be that 「ボール」 is already reserved for "ball". The former would just look a bit cooler to certain people, but as native Japanese-speakers, we all know that to pronounce 「ボウル」 in 3 syllables is highly counterintuitive. It will simply make you stick out in the Japanese-speaking world.