Although I see your point, there are many who need a hard drive bigger than 320 GB and that includes normal home users.. I've got a number of friends/customers who are DJ's that use, and need 1 TB hard drives every day... They store thousands of songs and videos on the drive and as should be, they make backups of their primary drive to a SECOND 1 TB drive, as well as to other removal tools. Some use a single partition because the data is found quicker and works smoother for them. Some use two partitions, one with the operating system and programs files while the other is used as file storage. Either way, it's not necessary to create multiple partitions on a HDD.
And although you may have not had issues with partitioning software, we see folks on these forums who had data lost on both single partitions and entire drives. None of the programs are perfect, Partition Master, Partition Magic, etc. so users need to be cautious before using such.
As it being "plain stupid" not to partition a drive, I'll guess you haven't had the same experiences the rest of us had.. As a system admin, the most common hard drive issue we have is with the entire drive failing. When a drive fails, which they all do eventually, it doesn't matter how many partitions you've got on the machine. A single partition works fine for most in the business world and also for most home users as well. It's personal choice as to which path to follow but it's certainly not "stupid" or "bull", nor does it increase your "security" by creating multiple partitions. Eventually, a drive dies. It might be a short time till such happens or it might be a long time but either way, drives fail.. Depending on the type of backup made for such drives, using the same hard drive as it's own backup location (your statement of "E" Drive as a tenative "Back-up") is doomed to cause problems when the entire drive fails. Routine backups to another drive, DVD, CD, flash drive, tape drive, etc. is the best way to be secure in your knowledge that your data will be preserved.
Hope this helps.
Grif