Apple pushing people toward BT could have backfired in two ways. People leave Apple because they are annoyed there is no headphone jack and 2) people buy non-apple B/T products. That is what I did until I recently got airpods. Either way if you are a high-end audio type of person, jackless phones may not be for you.
There wasn't much risk because they have that adapter, and the cost of switching platforms is quite high. So, I didn't expect it to greatly impact sales.
But, I think they have lost sales they just don't know about. For example, I haven't purchased an iPhone in a few years, and don't plan on buying one for another couple years (or longer, if possible), because since I bought my SE, Apple hasn't produced anything I'm interested in.
Plus, if they had produced a smaller form-factor phone with a headphone jack, I'd probably have spent $800-1000 instead of the cost of the SE. I suppose the percentage of people like me are thought to be too small, but we/they really have no idea how many of us there are.
For me, it isn't about audio quality so much. My main issues are that a Lightning connector isn't as reliable (physically) as a 3.5mm since I spend a lot of time listening to podcasts with the phone in my pocket. I'm also not interested in BT for extended periods of time as a health precaution. But, even that weren't the case, they are still expensive and you have to charge them (and they don't sound as good). Aside from not having cords, it's a lose-lose-lose kids of thing.