My main reason for preferring the SE over newer iPhones is the size. Low price is an added bonus, but if I could, I would pay more to get more bells and whistles.
Other reasons that I prefer the SE are the perfect case design, flush camera, Touch ID, and having at least one substantial bezel. I also like being able to occasionally use the aux headphone port.
Regarding the aux headphone port—bluetooth audio is a convenient option, but it is not a replacement for aux because of its lossy compression. They are different ways to connect for different purposes. I use the convenience of Bluetooth when I don’t care about audio quality. But when I do care I use wired connection—lightning if the sound system is compatible, otherwise aux. I would be ok losing aux if lightning became the new port standard across the board for all audio equipment. But that will never happen because lightning is Apple’s proprietary port. It would have to be usb-c. But Apple will never give up lightning. So I prefer aux stays.