Plum measures influence. If you are conducting research or funding research, you want to know its impact.
WHAT papers are everyone reading? WHO are the rising stars? What new TOPICS are generating excitement? And you don't want to wait for years to find that out. Research institutions want to quantifiably declare and measure their research output. Funding bodies want to measure the effectiveness and influence of the research they sponsor. Academic publishers need alternatives to Journal Impact Factor to recruit and retain authors.