Most good athletes are not thinking about winning as such they are thinking about how they can win - the driving force will always be how to win, how to be the best - there is no possible way to ever have sport 100% clean - so be it that it may be getting harder - or purely for the fact that more athletes are doing it meaning more slip ups - giving the illusion that it is harder but it is simply more people doing it, meaning an increase of people getting caught out.
In tested competition I would be willing to bet much less are doing it than previously.