Arch,
The 1.7`s are not nearly as bad as the 1.6`s used to be for this.
Also if you have your tank mounted high,, (over the wing tube ) and run a header tank, it`s worse
My tank is mounted below the engine under the wing tube ,I use no header tank system.
The 1.7`s will only flood if you set your airplane in the direct sun for long periods of time. and fill the tank to the tip top.

I use the little clamp on mine as a precaution but it`s not a big deal, unless you leave it in the car in extreme heat, and forget to clamp it. on the flight line,You can also remove the fuel line from the front nipple, and take the fuel dot out of the vent hose exit,, thats tee`d from the check valve, and put it in the fuel line ,if your afraid of it flooding,
Thats what most of the guys do around here running the 1.6`s

Earl Haury perfected the system you are using years ago , he had his very well done with the neat loop in the exit ect. it worked great for him, as I`m sure it does for you, it`s a product of habits and what we are used to doing But, to me,

The small effort with the clamp is worth it to me and the Japan team for a clean engine cowling
and to preserve a perfect airframe, or a japanese quality paint job.

The original question from you is why we use it, I was not trying to debate who had the better system so,,these are the reasons why we use it.
Bryan