Great question - the "universe" of venues we address is centered on peer-reviewed machine learning like ICML, ICLR, NeurIPS, COLM because (a) we have expertise in this area and so can therefore judge the quality and (b) it's all open access.
Therefore, the further you get away from the topic of ML, the less dense our coverage. Frankly, it's a tough to editorial choice to determine which research directions and therefore which proposals to include. ML is quite multi-disciplinary. And people who have a few papers in ML but many in (e.g.) medicine get upset when their profile is sparse. But we can't possibly produce good proposals in medicine due to its tendency to be closed-access.
Therefore, the further you get away from the topic of ML, the less dense our coverage. Frankly, it's a tough to editorial choice to determine which research directions and therefore which proposals to include. ML is quite multi-disciplinary. And people who have a few papers in ML but many in (e.g.) medicine get upset when their profile is sparse. But we can't possibly produce good proposals in medicine due to its tendency to be closed-access.