Your confusion confuses me, montiman! XD
I mean, think about it:
- Fluent speakers outnumber non-fluent speakers in professional translation jobs by a nearly infinite ratio. In other words, there is no such thing as a professional translator who is not fluent in either the one language or the other language with which he is assigned to work. When such a person does become employed professionally, he is usually exposed fairly quickly and fired just as quickly.
- Fluent speakers outnumber non-fluent speakers in amateur translation and fan translation jobs, too, although the ratios vary. Mainstream anime tends to scare away amateurs moreso than hentai does (a) because the vocabularly and grammar in pornography is much simpler to translate than that in mainstream media, and (b) because it is much easier to translate hentai in small one-man or two-man teams than it is to translate anime, and the smaller the group is the more likely the translator can get away with poor translations. (Fans complaining about poor subs are less powerful to get a TL fired than coworkers are!! But if you're a group of one, then you have only the fans to answer to: and you can pseudo-translate all day long.)
So first of all, you shouldn't doubt the fact that translators tend to be quite fluent (or at least have a modest understanding of the language in the case of pornography and hentai). Second, your question is essentially one of motivation. And this extends to fluent translators as well as to amateur translators. What are their motivations for translating hentai!? Some possible ones include:
- money
- fame
- doing nice deeds for others makes them feel good about themselves
- practice their translating skills
- bored, nothing better to do
- procrastinating on the job or at school
- they think translation is fun in and of itself
- they like to be challenged
- they don't want an inferior translation that they saw circling the internet to become popular and pollute non-Japanese speakers' minds
- they're doing it as a favor for the original artist
- they're doing it to piss off the original artist
There are lots of reasons. You are definitely correct that if a person's reason is money and money alone then he is never ever ever going to translate hentai or porn if he is fluent in both Japanese and English: because if he is fluent in both, he is going to seek a job which pays him much better than leechers online would ever agree to. (e.g. make $15/hr as a translator for a firm or make $18/hr as a translator for a publishing house, etc. Wages are fictitious but are used to portray how professional jobs outclass fan-requests in terms of money earned). Besides, employment comes with health insurance and other benefits -- you sure as hell don't see that coming from the internet leechers! XD
But plenty of fluent speakers and non-fluent speakers love to translate hentai into English and do so without asking or wanting any money in return. Personally, I relate to the bullet about hating seeing pseudosubs and rewrites circling the internet. It makes me cringe every time one of my favorite stories is "translated" by desudesu. I also don't like how disrespectful SaHa has become now that money and fame have bloated his ego and given him the false impressions that (a) he has some intrinsic "right" to not have his illegal scans taken down if the original copyright holder reports them for copyright violation, and that (b) he has the right to talk down to his audience as if they're a bunch of no-good morons, what with all the cursing and frustration he posts these days about no one reading his stickies. People like those two make me want to translate hentai for free.
But I don't have the fucking time, so I can't and I won't. I'll have to hope that someone else does it for me.
Also, I can relate to wanting to do authors a favor. I know, I know, they didn't ask for the favor and you could say it's piracy, but that's not true for pictures posted for free to publically-accessible websites of the artist's own. In other words, I like to translate (and have been on-again off-again working on translating) pictures that my favorite artists put up on their websites for the entire world to see but which have Japanese text that is required reading to get the full benefit out of the pictures. Sometimes they're jokes, other times they're stories, but every time the words are important and when English-speaking fans can't read them it means that they're missing out. And I don't want that.
And neither does the original author. (Seeing as they've mentioned it before on their blog!!) So yeah. Stuff like that makes a guy want to translate hentai for free. And while I'm definitely not fluent, I imagine that motivators like these apply to fluent people, too.