Why is the public transport (metro rail) in Mexico city so popular?

1- It only costs 3 pesos, the cheapest subway system in the entire planet. You can travel to any station no matter how far it is and don't have to pay more cash. 2- It's a lot faster to travel the same distance than by car. Mexico City has AWFULLY DREADFUL traffic. People aren't joking or lying when they say they've spent 4 hours in traffic for just a distance of 10 miles. If your destination is near a subway station, you on average will only spend 30-50 minutes getting there. 3- It encompasses a huge amount of the city. Sadly metropolitan parts in the State of Mexico have no subway stations. The 2+ million inhabitants of the Satelite area are stuck traveling by bus to the nearest station which can take up to 2 hours depending on traffic. However they are at least building a new subway line that will connect all of the southest stations horizontally. In the past you were better off getting off the metro and getting on a bus to connect from part A to part B or enduring a 1 hours detour in more northern subway stations to save cash. There's subway stations almost everywhere in downtown Mexico City which makes it very useful. 4- It's safe. After one accident in the 70's where two buses crashed against eachother, they now use stop lights indicating if a train is too nearby ahead and there's never been a similar accident ever since. The safest subway in the world. Save for the occasional person that commits suicide or accidentally falls into the tracks, there's never been any deaths. You will encounter petty theft, but the subway is far safer than taxis and buses that can get mugged much more easily. At least the subway has cops everywhere.