I've worked in the tropics for the last 19 years. When I first got here, it was suggested that I take a Chloroquin tablet once a week - pick a day and stick to it. I picked a day but found that I'd keep forgetting, so finally gave up the whole idea after two months.
Almost as soon as I started taking Chloroquin, I was told that it was better not to take anything. It was suggested to me that, no matter what you take as a preventative, it was still possible to get malaria. Therefore, taking any tablets for it was only going to mask the symptoms until it hit really hard. The thinking here, at the time - and even now - is that it's better to get the earliest symptoms, so that treatment can begin at the earliest stage.
If you've been using the "top shelf" stuff as a preventative treatment and still get Malaria - it happens - what is left to attack the malaria when you get it? Thus, it was always seen as important to use only Chloroquin, or something equally mild, as a preventative and also for initial treatment. That way, you can always go up to some stronger treatment, if necessary.
So far, I've never needed anything stronger than Chloroquin. I know that I've been lucky in this regard, but this is still the "fact of life" as I see it, in this part of the world. Probably just a case of horses for courses.
Hope this helps.