Being available in a niche market isn’t the same as being affordable because its a mass product. There’s more use-cases then you outline: they are particularly good for those with certain types of disabilities. You are right that mixing with traffic is another key reason why they arent as popular. There’s a reason you see them most commonly in areas with decent segregated infrastructure. Personally I have a DF for some of the reasons you outline. My point wasn’t all about the frame though that was just an example, its also true of the focus at component level where R&D has not prioritised low-cost low-maintance options because the high-cost high-performance market was more lucrative and that stems from in part from the direction performance cycling took.
Being available in a niche market isn’t the same as being affordable because its a mass product. There’s more use-cases then you outline: they are particularly good for those with certain types of disabilities. You are right that mixing with traffic is another key reason why they arent as popular. There’s a reason you see them most commonly in areas with decent segregated infrastructure. Personally I have a DF for some of the reasons you outline. My point wasn’t all about the frame though that was just an example, its also true of the focus at component level where R&D has not prioritised low-cost low-maintance options because the high-cost high-performance market was more lucrative and that stems from in part from the direction performance cycling took.