Why do some Hotchkis rear sway bars bolt to floorpan?

[Bandit]

I have a Hotchkis TVS on my car, and I am thrilled with the performance. However, one thing I was wondering, as I was wrestling around inside my car attempting to remove my rear seat to install mounting plates for the rear swaybar, is why do they have the mounting points bolt up to the rear floorpan?

Then, as I was drilling holes through my floor and trying to line up those mounting plates, and cursing profusely, I was wondering: Why do they bolt to the floorpan?

Now, as I sit here going through the suspension threads on this site, I am wondering...well, you get the idea.

Paul