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It's been around for a while, but it's trickled down to more boots and more shops are willing / able to do it.
When I was working in a shop it wasn't common that customers came with their own boots to rent just just skis, but whenever they did it was a fun lottery of what condition they'd be in. I had to reject a few customers because their boots were so worn or old we couldn't safely fit them to a binding.
About as much as bike tech. If you are on the higher end, looking at carbon touring boots for example, a lot has changed in the last 5 years. If you're looking for your first pair of piste boots, then the most significant change will be how comfy the liner feels and how willing even smaller shops are to heat molding them to your feet.