OK, let me try...
Ranking is achieved via competitive play. Best 7 or so matches are accounted. In my category, winning player of my level gives 20 points, 3 levels above - 100 points. Ranking for the new year is calculated based on earned points. Rankings are published once a year. There is a procedure to apply for high ranking, if someone did not play for a long time. Yes, all players with valid French Tennis Federation have ranking, even those playing in local leagues. I do not feel ranking is ignored. On the contrary, it gives a precise indication of player's level. I have played around 30 matches and never seen a discrepancy.
Now about ranking system in two words. Level 0 player here France corresponds, in my mind, to USTA level 6 player. Player with 1/6 level, need to start with one point advantage, every game out of 6, to play on the same level with level 0 player. Player with 5/6 would need 15:0 advantage in 5 games out of 6 to play equally, finally 15/0 player - 6 games out of 6 - all games in other words. 15/1 player gets 30:00 one game out of 6, 30/0 - all games. 30/1 player would need 3 points (40:0) one game out of 6. The lowest level is, therefore, 30/5 - 40:0 5 games out of each 6. Below that level the player can not be ranked. Finally, negative ranking (-1/6, -5/6, etc.) is used before a player gets national ranking.