This has been discussed in the past a bit:

• Couple of suggestions #2128
• Add these packages to ensure Bluetooth and ntfs partition mounting work in gnome. #1350
• Suggested basic default settings that are needed. #1307

And I think @dylanmtaylor summarized it quite well:

Not everyone wants BlueTooth enabled out of the box -- this is a user configuration item,

Especially considering even network is optional in KDE under archinstall.

Something I would be open for tho, is detection of bluetooth hardware (for instance via lsmod), and then offering an optional menu item post-install to setup bluetooth which could unclude the applets/packages to handle it. That way we don't include it for everyone out of the box.