AirPods... Granted i take calls on my S0 fairly often and you don't have it up to your face so long as you are in a fairly quiet environment. In other cases just use AirPods or whatever your favorite wireless solution is. If you're (the general you) someone who can't stand wireless.. it's time to get over it...
How assuming of you. I do actually own a pair of AirPods, I use them everyday. I am a believer in wireless, however the watch is still a poor device for calling on. I actually don't even have my AirPods synced to my Watch because I don't have any music on it. It takes too long to load and I have too much music for it to fit on there. Sure I could sync maybe 1-2 playlists, but then the battery becomes drastically more drained using AirPods. Plus, the Watch doesn't have a dial pad, so if I call a business that prompts me to dial a number I have to switch the call off to my iPhone. Then I have to re-connect my AirPods to my phone which takes at least 20-30 secs, sometimes as much as a minute depending on how finicky they decide to be that day.
The Watch is a good device to answer a call on in a pinch and say 'Hey can I call you in a minute when I'm free?' I'm not going to go phone-less just to connect my AirPods to the Watch, make an hour long phone call, then have to drop the watch back on the charger for at least 30 mins to an hour to get a decent charge. In fact, ever since I got the AirPods, I haven't really had to answer calls on my Watch because I usually always have one of the buds in.