What if there's something wrong with your disk -- would you really want it to try and mount it? Wouldn't you rather it boot itself into a stable state where you can do what you want, instead of making unsafe assumptions about your system?

It doesn't know what belongs where, either. Your /etc/fstab is usually what tells it so, and not having been booted off the same drive, it doesn't have your usual one. I don't understand what you mean by "dummy files". mounting is what turns a disk device into a folder full of files. Most UNIX/Linux systems don't bother mounting filesystems they don't recognize -- i.e. aren't listed in /etc/fstab. It has no idea what folder they belong in after all. My above sentence pretty much covers it. Partition editing has nothing to do with it. You never edit partitions in the normal course of accessing your data. No, to mount a partition, you mount it. It is done via the unguessably secret and hidden command name of 'mount'.

Code:

mount /dev/sda3 /path/to/folder