I agree, it is pretty niche and I belong to that niche. As a music nerd myself, it was dedicated storage and just being used to having music offline without the streaming services. The iPod nano was so tiny, that it felt like nothing is in my jacket's pocket. I do have some music on my phone, but it's photos that are mostly taking up its storage. I literally have gigabytes worth of music and also audiobooks that are several hundreds of megabytes each. Though I don't have data to support it, I'm also trying to conserve my phone's battery.

If you listen to music all day, saving phone battery life is a pretty good reason. Plus a non-Android MP3 player can get 40-100 hours on a charge.

> all the mp3 players I've seen are made to be as cheap as possible.

There are plenty of high-end players which prioritise sound quality and provide a better output than phones. The NW-ZX700 in the featured article looks to be one of these. FiiO is another well-known higher-end brand: https://www.fiio.com/m17

I wouldn't call FiiO high-end, they have a pretty wide range in most products (including DAPs) that goes from budget to relatively high-end ($1800). Astell & Kern start about one step down from FiiO's high-end, but can take you much higher (their ULTIMA SP3000 is ~$4300).

> There needs to be a good reason to carry extra device

Funny enough, for me that extra device is the phone: I see no reason to carry a "phone" for normal day-to-day stuff as my walkman has all the features I normally need (email, PDF viewer).

I want to carry it for other reasons as well: due to its smaller screen size, the walkman limits the use of addictive social media.

Main reason to use a standalone mp3 device is: doing excersie (sports, running, etc.). I cannot play, let's say basketball with my phone hanging around. Nor running, nor almost anything that implies excersising.