This is because it's designed to send a "signal" only, to the HID brain works, when you select the Brights from the inside of the car. The BLUE wire sends a LOW VOLTAGE feed so my High-Beams are underpowered.
Next, if I ever wanted bright lights again, I'll need to use the BLUE wire which I hooked up to the Hi Beam filament which is the prong on the RIGHT rear of the H4 bulb. Beautiful, nice and bright, just have to make sure to leave the fog light ring on the headlight switch turned to the on position from now on, then the headlight control works as expected. I took the GREEN wire that feeds the fog lights and hooked that up as the running light (looking at the bulb from rear, it's the LEFT prong, the TOP prong is GROUND). First, I bought those female crimp plugs, the large ones that fit the 9003 H4 type bulb prongs. But it's not a direct plug and play solution, so here's what I can share. Meanwhile my wife's 2007 with Halogen bulbs (which lit up the road just fine) was working perfectly with no such safety issues, so I thought, hey, why not pop these chipped faded faulty headlights out and put in a pair of new clear Halogen style units in mine? Happy I did.
And not being an extremely wealthy person, I wasn't about spending money on these expensive bulbs once or twice or ever. I got sick and tired of the left or the right or BOTH lights going out and having to turn them back on more frequently than ever on my 2004. But I'm sure you never thought that there might be a legitimate reason for wanting to change out these worthless lights before spouting off, but we've been fighting with these horrible headlights for 3 years now, and would LOVE to replace the crappy HID with halogen. I have to say getting stopped by cops when it's only 1 light out and it's not dark enough to notice kinda sucks too. So no, it's not a silly idea, it's one I'd do in a heartbeat if I could, before my wife crashes coming home from her shift at midnight. These stupid HID bulbs, at least in the 2008 Prius, last a fraction of the time of those wonderfully cheap halogen bulbs, and at several times the cost. One time both HID headlights and the fog lights went off at the same time on my wife coming home from work in the middle of the night. Usually, you can flip the lights off, then immediately back on, and they come on, but that second of driving in the dark on twisty roads kind of sucks and makes one long for "retro" headlights that actually worked when you turn them on. Sometimes you're lucky and it's just 1 light, usually the driver side, but other times it's both lights. This is a legitimate safety concern because Toyota refuses to do a recall even though the wonderful little HID lights have a very dangerous tendency of going out while you're driving down the road at night. This isn't a back-asswards request or a waste.