Why is it difficult for astronomers to accurately measure a value for the Hubble constant H?

Astronomers find it challenging to accurately measure the Hubble constant (H) due to several factors, including the reliance on different methods that produce varying results. Discrepancies arise from measuring distances to galaxies using different techniques, such as Cepheid variable stars and Type Ia supernovae, which can yield inconsistent values. Additionally, the expansion of the universe is influenced by dark energy and cosmic structures, complicating the interpretation of data. These factors lead to uncertainties and debates over the precise value of H.