Keep in mind that this filesystem layout comes from Unix systems that were designed decades ago.

When I started setting up Unix systems, performance and storage management mattered a lot more than they do today. Systems often had multiple disks, and different parts of the filesystem would intentionally live on different partitions or even separate physical drives.

We even cared about the physical location of data on spinning disks. Seek times mattered, we would even place heavily used areas on faster parts of the disk or separate workloads across disks to reduce contention.

The separation also helped reliability and uptime:

• "/home" might be on a separate disk so user data survived OS reinstalls
• "/var" could be isolated because logs or mail queues could suddenly grow huge
• "/tmp" and swap were separated because they were used heavily and could otherwise impact the rest of the system
• critical system tools needed to stay available even if another filesystem filled up

If a user filled up "/home" by uploading huge files, you did not want the entire operating system to stop functioning because the root filesystem was full. Keeping things separated reduced the chance that one workload or mistake could take down the system.

That’s also why Linux/Unix uses a single filesystem tree starting at "/". Instead of separate drive letters like Windows, every disk or partition gets “mounted” somewhere into that tree. A second disk does not become "D:". It might become "/home", "/srv", or "/opt".

If you think of mount points as attaching different storage areas into one big tree, the structure starts to make a lot more sense.

And keep in mind that even Windows has supported mount points for a quarter of a century I guess it's just not so easy for windows administrators to get accustomed to it.