Incent Download Generators - How are they allowed in Play Store?

Hello,

Anyone of the CPI experts around knows how apps like these are allowed in Google Play Store?

Free My Apps
CashApp
Cash for Apps
CashPirate
Quick Cash
Tap Cash

They are giving money / points for downloading apps.

It seems that many other apps that use similar techniques are getting removed over and over again, but these are protected somehow.

Any ideas?

Yes , mostly incentive apps removed from GP store , even they don't allow survey like pollfish.