Altmetrics are part of a wider conversation around the use of measures to try and capture the potential impact of research. They are not meant as an alternative to traditional indicators, but rather to be used in addition to traditional bibliometrics.
Research disciplines that produce diverse or non-traditional research outputs, and those that are slow to produce citation counts, can use altmetrics as a way to ensure these outputs are included in showcasing evidence of potential impact. And for all disciplines they provide a way to view the societal and economic use of research.