If legitimate voters do not have an aadhaar or if they could not link it due to any reason, they will be removed from the list. For example, some homeless people do not have aadhaar cards yet. In the 2018 Telangana Assembly elections, linking aadhaar cards with Voter ID led to the elimination of 20 lakh voters.
Eliminating cash completely may worsen the situation of some people such as poor people, digital illiterates etc. Moreover, it can be a threat to the right to privacy. So, a completely cashless society is not a good idea, at least for now.
For example, agricultural drones can observe the moisture in the soil using sensors. If it is below the predefined value, it will take the programmed action such as alerting the farmer or switching on the water spraying function in the drone. It will also result in more efficient use of water.