As someone who gets 25% extra time, I think it's perfectly fair for certain people to receive extra time. People who say to me it's not fair that I get more time often do not understand the reasons why I get extra time. I get extra time because my processing speed is incredibly low (my test result was below the first percentile) and because I find it difficult to concentrate (so if my mind wanders during the exam, I still have time to finish it).
I do understand however that indeed, it is unfair when people cheat the system to receive extra time. However, it is incredibly difficult to successfully do this, as you must have evidence that before the extra time you were underperforming and not finishing exams, have a low test score in at least 1 section that supports any disability you have, and mountains of evidence that after receiving extra time your exam results are improving.
In total, it took me 2 years to gather all the evidence I needed, so unless you fail exams on purpose for 2 years and fail the test on purpose, then you shouldn't be able to get extra time for no reason in exams.