Ek just for the record, I have occasionally had the same thought as you - why the hell am i having to learn this, and also, why the hell can't the JAA write properlythe answers, as far as i can tell, from discussion and debate with my instructors, is that we have to learn masses of stuff because the JAA have no idea what sort of flying you're going to end up doing.
If you were to end up flying DC-3's for a...err..."cargo" airline out of jungle airstrips in Bolivia or Colombia, then arguably it would be of great interest to know that whatever you do, lowering flaps beyond the takeoff setting ain't going to reduce your take off run, or that when you go to fill up your aeroplane hydraulics system with Skydrol, you open the tins marked 'skydrol' to see a mysterious red liquid in there in a barely prepared airstrip in Africa, you may be grateful! Of course, realistically, unless you are to be paid in large wads of used fivers stuffed under the door in the gents by a man wearing a white suit and a Panama hat, the chances of you ever needing to know this are minimal. Hence, we came to your conclusion, it's absolute !!!!!e on the most part. But it is useful whatever you fly that if something goes wrong you can help out the engineers by telling them what happened and having some understanding of the 500 mph deodorant canister's systems. May save the ginger beers time and your company money.
The language is because, for those of you that don't know, the database questions have been submitted by various nations, for example the Swiss make the met questions, the French i think do systems, etc, and thanks to the glorious paradise that is european co-operation, the fund for proper translators that can actually speak two languages, the translation tool used is a bad tempered 14 year old with a passing interest in language and a Collins French dictionary, and google translate when he's in bed. Hence terms like 'leakage current'.
To be honest though, I do find most of it pretty interesting, however for what most of us will realistically need in our careers, it does seem a tad excessive! Would be nice to know, however, that as I plummet towards the earth, that had I used butyl seals for my hydraulics system, instead of neoprene, my fluid wouldn't have poured out of now dissolving seals, or that I shouldn't have gone flying knowing that my oxygen bottle was only charged to 1400PSI as I collapse to the floor having discharged a BCF extinguisher onto the flight deck. Which, for those in the know, is the most common form of fire extinguiser used in aviation!
Good luck to all of those putting themselves through it!