Quite a lot of people do look into sources, actually. Quality of those checks, and how much do they cover in the end - that is the question. But it is better th

Quite a lot of people do look into sources, actually. Quality of those checks, and how much do they cover in the end - that is the question. But it is better than nothing, and absolute majority of closed source apps offers you exactly nothing in this regard. Surely, opensourced code is not inherently safe, but with time passing, while userbase is big enough, it gets some attention, which means advantage on a scale of probabilities.