1. Practically, if we need to frequently write proposals and papers, it's
critical to follow the latest studies in the field. We don't have to read
the whole article, but should be familiar with the methods and results. Only
those highly established PIs like 11G, who obtain their funding through
different sources or have subordinates manage their research progress, can
have the leisure not to keep up with the literature.
2. If one truly cares about science, he/she would want to know what's going
on, whether or not the knowledge is "useful". I've seen many retired
professors who read more than aspiring researchers. To me, a true scientist
does things out of curiosity first, like a kid. In addition, we can best
judge a person according to what he/she reads when the reading is not
demanded by work.