Inductive Device Triggering

[Kind of Blue]

I do not know why these days, that invasive methods like cutting or "tapping" into live wires, such as supply for high or low beam, when for example driving lights are being set up and integrated, when less invasive methods such as induction are available. Modern vehicles are so sensitive to any disturbance and original wiring looms and such built down to the lowest possible cost and current carrying capability that surely it is not best practice. Of course it has been standard practice for years that in order to trigger relays and such that a suitable tap it taken but why?