As someone who roots single-purpose Android devices, this is one of those things that sucks big-time but makes total sense.
The only reason one would unlock a bootloader is to root the system partition. It is impossible to protect data on rooted phones and makes data exfiltration attacks significantly easier to do.
This is a huge problem for banking and music apps that absolutely rely on this capability. Samsung is, by far, the biggest seller of Android phones in the US. (I think Xiaomi is the biggest globally), so they are under much more pressure to clamp down on this.
That said, rooting Samsung devices has been a worthless pursuit for a long time. Doing so irreversibly (via eFuse) disables KNOX, which prevents DeX and Samsung Health from working. It also trips SafetyNet, which disables a whole suite of key apps (banking apps and Apple Music don't work; not sure about Spotify). There's a Magisk module that uses well-known device IDs to work around these, but these only work temporaily. Many people have also reported issues with the camera (a popular reason for buying Samsungs in the first place), and you no longer get OTA updates. I believe you also get degraded camera performance if you flash another ROM since the device module is closed-source and relies on One UI to work. This is before considering that stock ROMs have gotten really good over the years (especially Samsung's), and many of the reasons why we had to root have mostly gone away.
You can work around this by buying a Pixel for now, but I think we're a few years away from bootloader unlocking going away entirely.
That said, I stll root Android devices that will only serve a single-purpose, like my BOOX eBook readers that I use Firefox on. This lets me run AFWall so that I can block network traffic for everything except Firefox (and a few other apps). However, I won't be logging into my Google account on them, and they aren't ever going to run banking apps or anything like that.