It’s cheaper than you might think. Much like in gaming, there’s a lot of people who really want to work in the anime industry, even if it’s just on the localization and distribution side. This drives down salaries quite a bit.
Someone who knows English natively and Japanese sufficiently is necessary for producing quality subtitles; it's arguable that potentially having slightly less accurate subtitles (i.e. missing nuance) is better than having slightly less fluent English (i.e. not communicating in a natural-sounding manner).
It's not just about translation, after all, but localization. While you can (or kind of have to) assume some level of familiarity with Japanese life/culture for someone watching anime, it's easier for a native English speaker/someone who grew up in North America to notice cultural disconnects and figure them out.
An example I once heard: a book in Italian might say the character "ordered a coffee" and then "picked up the coffee, drank it, and walked out of the cafe". An Italian without as much consideration of American culture might translate that directly, but someone who understands localization would know that Italian character ordered what we would call an espresso, and know to change the text to be specific; otherwise, it sounds as though the person is guzzling an entire mug of black coffee on the spot, which would likely come across as psychotic and unnerving compared to taking a single shot of espresso.
Likewise, an Italian reader of an American novel might be unable to comprehend how or why an American character could spend 20 minutes nursing a cup of coffee, because they might be picturing a 1-2 oz espresso rather than a drip coffee.
So yeah, that's the big part of why it can't just be someone who knows English to some sufficient degree - because without fluency in spoken and written English, familiarity with how things would be said in English, and cultural differences between Japan and North America, you're going to end up with all kinds of dissonance.
Not unheard of, but probably harder than hiring for a call center, and more need to prevent high rotation due to difficulty in finding replacements.
Edit: not that I disagree with your general idea, just pointing out potential issues.