The single chain ring is a trend across many bike brands and models, not just ebikes.  It simplifies and lightens the bike.  This works esp well with the new wider range 11 & 12 speed cassettes.
That aside, I've owned both hub and mid-drive ebikes.  I converted a MTB to the hub drive bike selecting the components to get enough torque to climb around our hilly little town.  It worked fine for some years.  I did occasionally use the 3 ring setup, but never the smallest ring.
When it came time to replace the DIY mid-drive I test rode quite a few bikes and was attracted to the mid-drive for lower overall weight, better balance, and hill climbing.  At first I focused on brands that offered 2 chain rings, but found that the 1x setups worked better than I expected.  After a year I don't regret going with the 1x mid-drive.  Plenty of torque.  The 1x11 gearing works well on most trails even without electric assist. 
BTW - Neither of these bikes would have gotten me home without electric assist.  The hills are too steep and the bikes are still heavy...
