There is no clear answer as to why workers are still needed in your cities in Cities: Skyline, you should always keep an eye out on the following points. There can be multiple reasons causing the issue and if you come across something we missed, make sure to let us know in the Comments Section below.
Regulating RCI Zones
One of the first things that you need to check is whether the residential demand is being fulfilled or not. Always check if residential is high enough to require more Residential Zones and do so accordingly.
Regulating Literacy Rate
Commerces, industries, and offices require workers of varying education levels – some higher and some lower. You will, sometimes, find yourself manually keeping the literacy rate of your city low to match the demands.
Therefore, it’s always a good idea to check the demand of buildings. Build more schools, colleges, and universities if your literacy rate is falling short. Also do note that overeducated citizens will also work in industries but only as a last resort.
Enabling Free Flow of Traffic
The most common reason is when workers are unable to reach the workplaces in time. You need to ensure that there are multiple routes to a particular workplace with more than one transportation means available.
Aside from buses, make sure that metro or trains are also reaching the working area. Lastly, bus lines need to cover a chunk of your city. These bus lines not only need to pick people up but there should be more than one reaching the working area.
Found anything misleading or confusing? Let us know.