One big problem is that pretty much all of these devices have major downsides. For example, I don't know a single repairable or rugged phone with an actually really good camera or a flagship SOC.

They also usually have a huge markup and are often produced by small boutique manufacturers with terrible support (like Fairphone) and/or really bad software (like Fairphone).

So if you have the choice to e.g. pay €600 for a Fairphone with its terrible camera, battery life problems, inexistent support, huge amount of bugs and frequent issues with network providers (e.g. VoLTE not working), or you pay €300 for a comparable Samsung with similar software support duration (6 vs 10 years) and it just works without issues.

If there was something like a Samsung A56 or even a Samsung S25 that's nicely repairable and costs a maximum of €100 more than the regular version, that might be worth it.

But the way it is now, it's much better to buy a regular phone and spend the €300 you saved on 1-2 professional battery replacements down the line.