I wanted to see how necessary commercial and industry are in a city. As far as I know, they are only used to drive up the RCI demand. So I ran a little experiment. With the help of the Super Demand Mod (as well as the money and unlock all mods), I built a town using only residential and civic service buildings.Here is what I have.As you can see, other than the income being in the negative and the 99% unemployment, the town is doing just fine. The citizens are pretty happy and crime is low. Since barely anyone has jobs, there's almost no civilian traffic, other than the ones that work in the service buildings and emergency vehicles. There are no schools, however, nor commercial or industrial lots, yet the citizens don't seem to mind much.After spamming some schools, I got these results.Here, the population has almost doubled, and my income skyrocketed. I'm now making more money than ever. Happiness increased slightly and crime stayed roughly the same. Almost all buildings leveled up to level 3. Unemployment decreased to 83%, but that is likely due to the jobs the school buildings provide. Also, even when the residential demand was at zero for several in-game years, people were still moving in.So with this, I have a few questions; with absolutely no industry or commercial stores in this city, where is the money coming from? Why are citizens just fine with being unemployed, or having no places to shop? Where is the economy?I think this is an issue that really needs to be addressed. It's bad enough that citizens don't even have to travel to work, let alone get there on time or even have a job, but for them to be completely happy with no commercial buildings to shop in, or even parks to relax in, it's really concerning. It shouldn't be possible to have a thriving city with only residential buildings and service buildings.Here are my suggestions:1. Make it so that cims have to get a job. If they remain unemployed for a period of time, then they should be forced to move (unless they are pensioners, kids and teenagers, or anyone that lives in the same household as someone who has a job).2. Have the cims require access to stores. Honestly, how do they live without needing to buy food?3. Have buildings only be functional when enough workers are present. This could also solve the issue of cims not needing to get to work at all, and drive the player to make sure they get there on time. Cims should also lose their job if they miss work too often.4. Social classes should be introduced to make the economy more dynamic. Cims who work higher positions in their workplace would have more access to higher quality goods (in this case, sold in lvl 3 stores) than poorer cims.5. In order for this to work well, a functional day/night cycle is just as important. Cims must have a consistent workday/weekend schedule to simulate these effects correctly. They work during the morning, return home in the evening or go shopping or visit leisure venues, and have free-time during the weekend. Some workplaces (emergency service buildings for example), would have some cims working nights and/or weekends.That's all for now. I hope that I at least shed some light on this issue. I would really like to hear your input and what you think about this issue.