[meerita]

Simply: side projects trains your skills in other areas that your current job don't.

[mhndrcksn]

Great point. I wonder, is it more about diversifying risk (employability, keeping up with new tech)? Or the pure pleasure of learning? Both?

[meerita]

Well, the point is, if you want to make a side project, it is because you have a strong reason. It could be several things, among them, learn new things, solve problems or simply the mercenary way: win more money.