This is interesting. An awful lot depends on what the issue is. Stuff like womens right to vote, sit on a jury, etc.,etc., would never have happened unless someone was willing to take on the State with all its might and bear the consequences. A test case can be taken by anyone affected by a particular issue BUT either they must pay for it themselves ( and you have to remember that unless a person is willing to be a lay litigant) that that means paying lawyers ( and I personally see no reason why I should work for free!) or asking the lawyers and them agreeing to work for free.
I have had situations where I have been asked to take on "public interest" cases. In most cases, they were not public interest but very much a personal interest with a complete inability to concentrate on why they should expect lawyers to work for nothing. Daw!
Organisations like FLAC and the Coolock Community Law Centre amongst others do fantastic work but it is largely down to the phenomenal commitment to social justice of the people working there.
mf