BUT, let's say you decide to allocate 10GB to /, 4GB to swap & 1GB to /tmp. Suddenly your / partition is full and you can't install more stuff. With LVM you can quickly shrink /home and increase the size of /. All on the go without having to reboot. I found this very handy while working on a Windows VM installed on my home PC, which was busy doing some video rendering and I didn't want to stop the rendering to increse the / partition.
Just a note to say this behaviour is dependant on the filesystem on top of the LVM logical volume.... Some (most?) will require you to take the mounted volume offline to shrink with not all allowing online increasing of size... so it is important to double check the documentation for your filesystem before carrying out such an exercise whilst the volume is mounted... and of course as with any changes to partitioning information and volumes ensure you have a backup of the data when resizing (especially shrinking) in case of any corruption or issues in the process....
James