Because Microsoft acknowledges a performance advantage to locating the paging file off of the boot partition what is the main reason that the boot partition is its default location?

I'm not Microsoft, nor am i affiliated with them in any way, but I imagine their reasons are similar to these.

1. Ease of install. Not everyones needs are identical, some may need larger paging files (and thus paging file partitions) others may find they are more concerned about hard disk space than performance, so theres no one-size-fits-all solution. Therefore it would be necessary to add more partitioning and page file configuration dialogues to the install process which would confuse the less savvy.

a. The people who are more savvy already have the know-how to alter their partitions and reconfigure their page-file.

b. The people who are less savvy tend not to tax their system to maximum performance, and thus less likely to appreciate the small performance boost.

c. The people who are less savvy may be upset when their hard disk size is smaller than advertised (due to the swap partition) and may not understand the reasoning behind it.

d. People who are less savvy may see the separate hard disk letter, and not understanding its purpose, fill the partition with user data & severely reduce their system performance.

2. Longevity of hardware. The paging file obviously gets a lot of reading & rewriting, nearly constantly in fact. Putting it onto a separate partition concentrates this increased activity to one area of the physical hard disk, this could lead to early hardware failure.