But why inevitable? Well, all chains stretch over time and 1100km is quite a distance for a low quality chain on my Schwinn. And since my bike has a 3-speed internal gearing hub, there is no chain tensioning mechanism such as a rear derailleur. This means that frequent adjustments of the rear wheel position should be done in order to tension the chain and prevent dropping. I must admit, I forgot about it and haven't done it for the last few months. I blame it on my relative unfamiliarity with single-speed bikes (or IG hubs). The last time I had a bike like that was about 20 years ago. All my recent bicycles had rear derailleurs, until I bought that Schwinn.
I will keep an eye on it and will likely replace the chain after riding another ~700-800 miles. By then it will be completely worn, especially since I ride on hills everyday, pushing harder on pedals, which may stretch the chain more than if my commute was completely flat.