I've made this point before but I'll repeat it. In BtS Nationhood is not just about drafting. It is probably more suited to a SE type of economy than a CE. I'd say it is better for a domination style game of expansion rather than used defensively for a builder style game.
One reason for adopting Natiohood can be the +2 happiness which is very useful in your largest cities when combating WW or Emancipation. For many cities 2 extra pop is a very significant boost and without many towns is better than Free Speech and in an empire with lots of cities it is better than Bureaucracy (and a cheaper civic than both).
Then there is the +25% espionage which can make a big difference in the middle game if you're pursuing that as a method for making your victory easier. It means each of your spy specialists give 5 EPs rather than 4 and that encourages you to run them. Before jails it is the easiest way to boost all your cities EP output (and jails have to be built costing 120 hammers each). After jails and security agencies have been built, and they give a combined +100% EP effect, its +25% is still useful as it boosts the passive outputs from these buildings. I find that running Nationhood at the time it becomes available in the game (I often take it as the Liberalism free tech) makes getting enough EPs to see the power curves and research of all the other civs you meet (following Optics revealling the other continents) very easy. I seldom have to spend commerce on boosting EP production; courthouses, jails and a few spy specialists provide sufficient.
And then there is drafting. Drafting Janissaries or Redcoats or Toku's gunpowder troops are well established ways to win a game. But without the inherent advantages those leaders have drafting is still a powerful strategy. Even if the main cutting edge troops are cannons from Steel or cavalry (Rifling and Military Tradition) then drafted musketeers and riflemen are excellent back up troops providing bulk and strengthen my SoD and up to date garrisons. My military often falls behind while I beeline the research and old axemen and archers would cost a lot to upgrade. Drafted troops provide a great stop gap at the best possible food to hammers exchange rates. A drafted rifleman effectively costs 37 hammers instead of the 110 if built through Slavery and normal production, so Nationhood can be seen to inject up to 210 hammers per turn (3 drafts saving 70 hammers apiece) into the game which is much more than Bureaucracy can ever do.
Putting it all together, drafting (of riflemen in small cities), +2 extra happiness and +25% EPs for a civic with zero cost is a good deal for a SE style game bent on expansion. It is much more than just the drafting although that could be reason enough. I like to use it as part of a strategy to leverage the technological advantage from the traditional beeline to Liberalism. The happiness lets your cities deal with the WW, the espionage helps you pick a target and predict trouble from neighbours and the drafting provides the muscle. At that stage of the game and used in that way Nationhood is arguably the most powerful civic.
. Plus I have a kind of avertion to it because I'm twisted (Police State ftw).
(usually from 5-10 settled GP) in my capital, so beaucracy or free speech are basically always > nationalism. In cases of AI "sneak attacks" or w/e I've always had enough defence and 90% of the time a large tech advantage that a few upgraded units will fend off the initial attacks fine. But thats just me and my playstyle.
