It's hard! A lot of it is, like I said, reputation. Sources of safe pirated and cracked software are maintained mainly through word-of-mouth - The crappier and dodgy sources will always invest into SEO to get to the top of the results, and are more likely to avoid legal trouble as companies appreciate that malware-infested installers actually help discourage new pirates.

Also, there's generally little incentive to go beyond the basic modifications. Most online scams, even outside malware, cast the net as wide as possible and even go out of their way to avoid complexity. They get the most money out of scamming new and uneducated users who pay up quickly. The same logic means they want advanced users to know it's a scam to avoid wasting time on targets who won't bother paying anyway.

I bet there are exceptions to this rule, but since scamming and malware are such low-profit ventures there's a lot of incentive on quantity over quality.