Mottled Houdan are listed as threatened by the Livestock Conservancy which means less than 1000 birds left in the US and less than 5000 globally at the last census count.
That might change as we are currently winding down 2020 census count, but truthfully I expect them to slip to critical at some point in the future. If we can get Polish enthusiasts to consider Houdan there might be more of a demand.
2 things were against them when they were imported to the US in my opinion. The flooffy crests were thought of as a novelty but impractical and the fact they don't go broody. Back then it would have been to much hard work to keep the breed going for small family farms.
They lay a white egg as often as a leghorn, so that is a huge plus in my book. Have a decent size to them making them dual purpose and are calm and gentle. All good traits.