Recently I have seen a few posts postulating that not all AT3s had electric start.  I can attest to that.  My first bike at 12 years old was a very secondhand 1973 Yamaha DT125 (AT3 across the pond).
It was a UK model and had a dealer sticker still on it.  Padgetts of Batley, my then local yamaha dealer.

It most definately did not have a electric start, nor even a starter button on the switchgear.  Over the years I thought that someone had removed it and fitted hardware from a CT3, but I have come across a pic of another one, in the same colour as mine with exactly the same cases.

Photo proof.  AT3. Kickstart only.

Yes, UK (and Europe?) didn't get the electric start on the 125.

I've no evidence either way to indicate whether the handful of 1973 models that we got were AT3 and CT3, or just both DTs. Either way, they were and are very rare - I've seen the odd UK 1973 175 come up on fleabay.

We didn't get electric on AT2 or AT3 in NZ [well i never saw one at the Yam dealer where i worked], just AT1 electric start plus kick only option in pre reed valve. But we had electric in "74 DT125EA of which i had one. I lived a sheltered life lol so someone might show AT2-3 electrics were around in other areas of NZ but don't think so.

Most info is on USA models. I always try to be clear that in the USA the 125 Enduros from 1969 to 1976 were all electric start versions. ONLY in the USA.

This is absolutely not true for the rest of the world. Other countries had "kick start only" versions of the 125 Enduro (aka Trail) during those years.

The tricky part is that in 1974 Yamaha redesigned the "kick start" version of the 125/175. Engine mounts and shift mechanism changed drastically. So if you have 74-76 (or so... some countries had twin shocks beyond 1976) non-US model, you may find the US 1974-76 parts lists for the DT175 might match better than the 125 lists. Unless you're lucky enough to have a "non-USA" parts list for your non-USA kick start only twin shock 125.

What I said above is also true for pre-74...  the USA 175 electrics parts lists should be close to the non-USA "kick start only" 125.

I never fully understood why Yamaha thought e-start was needed on the 125. My first real bike was a ‘71 AT1-C. I was pretty young and pretty scrawny kid, but I preferred kickstarting it. I suppose it was perceived tougher, but that bike started really easy. As opposed to the added complexity…

Yamaha cut their teeth on small trail bikes in the 1960's...  some of the 50cc models had electric start.  

It seems easy enough to kick start when we were kids and still now as adults...  but using a kick start is often extremely awkward for the uninitiated. (And perhaps nearly impossible for a hunter after stalling on a difficult trail while balancing a rifle and perhaps a kill strapped across the rack.)    And back then motorcycles were NOT mainstream... there was definitely an effort to make riding as easy and fun as possible for all genders and ages.