Downloading apps off app stores is easy. These sketchy websites can actually be real useful when developers decide to geolock their apps (i.e. when a local ride sharing app won’t download because your Google account isn’t from the country you’re visiting). apkmirror has also helped me obtain various Google apps that didn’t come with my phone’s custom ROM, though that’s one of the good ones that doesn’t alter apps.

Many of the sketchier will take apps and alter it to inject malware, though. By removing in-app purchases/ads/DRM with tools like lucky patcher they can explain away why people’s phones are calling these apps malware (because the alterations are to be expected), but the goal was never to give people free stuff, there’s always money behind it.