"Why buy the Clarity over a Volt
One reason is that one simply prefers the Clarity to the Volt - all the 'personal' reasons. Size and "Cachet"/"Reliability" ("I prefer a Honda") have been mentioned, but there *could* be : finish (interior 'quality' or 'feel'), appointments (collision avoidance, auto-braking, better mobile app, style/setup of infotainment), other options not available on Volt), visibility, the car's 'look' (which is very personal), color choices, seating comfort/legroom, etc., etc.
And, of course, the Clarity might have a built-in GPS system - which for some people is so important as to (almost) be a deal-breaker!!
My next 'ICE' vehicle will most likely be a plug-in hybrid. I want a minimum of 30 miles electric range (I may go down to 27 or 28, but grudgingly). One of us in the family will (generally) only drive 20 miles or so in the day, while the other will take the BEV (range 80-130 on freeway, most likely). And the PHEV will be the 'travel car' - the one we take on road trips (so I can get rid of my older ICE vehicle, which barely serves, currently). My other 'personal need' is that the gas engine must be a low polluter - comparable to (say) a standard Toyota Prius or Honda Civic hybrid (or better). A higher pollution Range Extender vehicle wouldn't work for me, as this would be the 'go to' vehicle for our road trips. A 'want' would be a hatchback, because we occasionally haul a kitchen table or set of chairs, or wine fridge, or buy a TV - and our Ford Focus fits that bill just fine (with rear seats folded down).
A number of auto manufacturers are blowing the "we want a large % of our cars to be electric before 20X0" horn. Honda is saying so (made announcements), as have others. A bunch
of plug-in vehicles (either pure electric, or hybrids) should be hitting the market in the next few years. Kia/Hyundai (similar to GM/Chevy/Buick/...) have already announced quite a few. There's already the Ioniq, Sonata, Soul, Optima, and Nero, and the newly announced "Stonic". The VW conglomerate is also making similar noises, but with fewer solid announcements so far (or at least not ones that I am aware of). As well as other manufacturers. It looks like non- 'conformance' vehicles will be available from quite a few manufacturers soon. I am looking forward to test driving them.