Endangered species are the tool the ecowhackos use to stop development/use of any kind in its tracks. It is the duct tape in their toolbox, used against everything from oil exploration to private property development, so long as it isn't their property.
Frankly, as long as the balance in the system is maintained, the specific species may not matter as much, and the tendency to rate subgroups (like the northern and southern spotted owls) as separate species is a highly questionable practice, but it allows for assessments of reduced numbers.
One recently listed here was the Dakota Skipper Butterfly, so listed because, well, there aren't very many of them. Oddly enough, the 1910 survey of the State mentioned that there weren't very many of them then, either. (IOW, about the same prominence as back when, despite ranching and oil and gas activity). Just because some critter isn't prominent, doesn't mean it is endangered.