The US national electrical code for 2011 changed requirements to say that there should be a neutral at each light switch box. Prior to that it was optional in order to meet NEC requirements. It is still not required that you go back and add neutral to an existing switch box, it only applied to New construction.
Some states or cities make NEC recommendations their local law. Others only adopt it partially, or add specific variations. Or take several years before they get around to adopting new versions.
Right now, most houses built before the 1970s in the US probably don’t have neutrals at all light switches. Most houses built after 2000 probably do. In between it can just be a mix.
As far as SmartThings-compatible light switches that don’t require a neutral, as of 2018 there are a lot more choices than there used to be. Lutron Caseta is one of the more popular choices. Some Z wave manufacturers make some in wall micros that don’t require a neutral, in particular the Aeotec Nano dimmer and the Fibaro dimmer 2. There are also some smart switches that fit over the top of an existing switch, so the wiring is irrelevant. All of these options can work with either LEDs or incandescent bulbs.
There are also some older model switches that don’t require a neutral wire, but that will only work with incandescents. And one current model GE Zwave switch that works the same way.
So now this is much less of an issue than it was even in 2017. 