I was also thinking about 7 speed supply recently (but more focused on Freewheels). Perhaps 7 speed was short lived compared to 6? And there are so many 6 speed bikes out there with owners who want to "upgrade" to 7 win a mega cogset.
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I don't do: disks, tubeless, e-shifting, or bead head nymphs. But I do hate all e-bikes.