That's not the case at all. These kind of Trojan operations are fly-by-night setups, and have the advantage of being able to react far faster than the official Devs. By the time you as the dev even know of the app's existence, they've already infected hundreds. And when you do get round to filing a takedown notice, they'll be back up the next day under a different name.

Even Nintendo can't get copyright infringing shit off Play Store in any fast capacity. Heck, Google will even run ads for people blatantly breaking copyright laws.

Edit: and that's before considering that Google won't let them onto play store and being only source available excludes them from eligibility for official F-Droid repos. They're going to have an absolute bitch of a time dealing with fakes and Trojans, even if they didn't release the source code at all