So many of you are complicating the issue. The problem is this. Some people do have an inherent advantage over others where languages are concerned. However it would be difficult to draw a line which states that these advantages make the situation "unfair" and restrict native speakers. Ultimately, every single person will have an inherent advantage at something, and even if you say "well what about the people who work harder", even that can be analysed as "ability to work harder and not lose concentration" or whatever. Ultimately, it's unfortunate but you will always be up against people who are better than you at something.
It's like going for a job and getting it because you're a native speaker of a certain language and the other applicant isn't. The other applicant may complain that you had an unfair advantage because you were a native, but isn't that the same as complaining that you had an unfair advantage because you were better at Maths, were more articulate and so on?
Ultimately if you are concerned that they will have an easy paper, this paper may still not be of value to any employer who wants to see evidence of effort rather than mere abilities (which are of course important too). Hate to go down the PE teacher "personal best" route, but it really is about that what you can do to make yourself shine. If you are not a native speaker and you learnt to speak a language, that will be more impressive than a native speaker who declares it but already knew it where effort is concerned (and effort is rated highly amongst employers) but as far as merit goes, the native speaker is much better at the language so if the job is language-based, will be in his right to get the job because of it.
As for WHY a native speaker would take the A Level, I think one should stop being bitter and jealous and concentrate on themselves. Who cares why they took it? If it helps, good for them, if it doesn't so be it. I don't know why anyone would do a degree in tapestry but we're all different and want to achieve different things. Finding no reason why they should take the subject isn't to say they did it maliciously or to make things difficult for you.
Hope that made sense, it's not something I expected to type at 4.10am!