It's a signal. Signals are important even if futile. Without such signals, we can only make assumptions concerning where the minority party stands on whichever issue.
It also forces Congresspeople to publicly take a stand and not just sit idly by and let Ajit Pai do the dirty work. Getting people on the record is important anytime something is being done at the behest of a limited number of corporations and contrary to the interests of their constituents.