It is really Apple's fault - they released a half-baked SDK with the first WatchOS, so people jumped on it, and put in resources to build apps. But they were terrible because they required a round trip connection to the phone for literally everything you see or touch. So the apps were bad, meaning nobody used them.
Then WatchOS 2 came out, and released with a new SDK that allowed for more processing to happen on the watch itself. Unfortunately this change meant apps had to be rewritten. At this point nobody was seeing any benefit from having a watch app, so they didn't want to waste developer resources on a platform that isn't going to bring any competitive advantage.
Basically a chicken and egg problem. The first WatchOS should have just had no apps until they could do it right.