When I took my school exams we didn't do coursework. It was a case of all or nothing written papers in the school sports hall at the end of fifth and upper sixth form. If you didn't do very well then there was the option of re-taking in January, or even the following May, but those re-takes would be the entire exam, not just a single paper.
Nowadays things have changed. A-Levels are split into AS and A2 sections and there is a large amount of coursework in both GCSEs and at A-Level. There are differences of opinion as to whether these are a good thing.
However, one change that I think is less positive is the chance of students to re-take individual modules up to three times during the period of the course in order to bump up their grade. Students who take a module in the first term of the first year of study (out of two) can re-take that module in the May, the following January and the following May if they want to. Later modules can be re-taken less, but I think you get the point.
A student who gains an A-grade for every module first time round will emerge with the same ultimate mark as a student who has re-taken section after section bumping their score up from a C, to a B and finally to an A. Whilst I applaud their determination, I don't think they could be said to have done as well as the student who got all the As first time.
So is this the reason why A-Levels grades keep rising? Certainly it seems likely to be part of the reason. Whilst I am all in favour of students being able to re-take exams, maybe during the two years of the course, it should be clear to universities and employers how they got those grades to enable a fair judgement of what the results really mean.