Why is research being done on SARS-CoV-2 virus in wastewater if it is not indicative of viable or infectious viruses?

In the Netherlands, but also in other countries, samples are collected from the sewer network to detect hereditary material of the COVID-19 virus in waste water with the aim of using the sewer as a mirror of the population. The entire city can be screened with one sample using the sewage water that arrives at the wastewater treatment plant. For example, sewage research can help determine how much COVID-19 occurs in the population and whether it is increasing or decreasing. One example is the work done by KWR laboratory and presented in Medema et al. (2020) study.