It's not a particularly recent idea, I believe Brompton has been doing that for decades. And it fills a very specific niche.
On most bikes I don't really see the point.
Either you want the convenience of an internal gear hub and you have plenty of options that offer a pretty wide range. For instance the Nexus/Alfine 8 feels plenty enough for a commuter bike even if you live in a hilly place. If you're rich you can go with an Alfine 11, Rohloff, or Pinion.
Or you don't want the weight/cost/inefficiency, nowadays you can get affordable and reliable 1x10 or 1x11 groupsets. And of course on a proper road bike you'll still want a double chainring.
The Brompton system is ... weird. Owing to the fact that the bike folds and the length of the chain line changes dramatically when you fold it, a traditional parallelogram linkage derailleur wouldn't work.
Instead, they have a crazy custom thing that runs the chain through a little pivoting fork that shifts the chain left and right on the two speed freewhatever[0]. The six speed adds the three speed internally geared hub. You can also get one or the other alone.
I believe they developed that combination when the supply of 5 speed hubs that fit their highly non-standard read hub spacing dried up.
I have a two speed Brompton and love it, but their engineers are next-level crazy in the best possible way.
[0] I wouldn't even care to guess. Everything they do is insane.
that combination system i've been talking about is for proper road bikes.
> And of course on a proper road bike you'll still want a double chainring.
why? the IGH replaces the front double chainring. weight and price might be a bit higher but it's probably more robust, less maintenance and you can shift under full load.
Still, I'll believe it when I see it at amateur cycling clubs. At pro-level I don't think anyone would take the performance hit (even though they claim it's compensated) just to avoid having a front derailleur.
For gravel, cyclocross or even casual road biking, if a double chainring really bothers you, then 1x12 groupsets exist.
On most bikes I don't really see the point.
Either you want the convenience of an internal gear hub and you have plenty of options that offer a pretty wide range. For instance the Nexus/Alfine 8 feels plenty enough for a commuter bike even if you live in a hilly place. If you're rich you can go with an Alfine 11, Rohloff, or Pinion.
Or you don't want the weight/cost/inefficiency, nowadays you can get affordable and reliable 1x10 or 1x11 groupsets. And of course on a proper road bike you'll still want a double chainring.