Can't see why someone would think a simple LED torch ( flashlight ) wouldn't work as a bike light. Lot's of choices if you want a decent torch. As a torch collector I suppose I have a good number to choose from so I have an advantage over someone who just picks any old cheap torch and then want's to bee-itch because he bought a POS.

My favorite for the bars is the Convoy S2 I bought from Gearbest. Though it is one of my more inexpensive torches it works great on the bars. The one I have is using a shorter reflector and thus the beam pattern is more spread out ( but not too spread out, still has some decent throw. ) I use mine as back-up when I go MTB'n. The spread with mine is so good that sometimes I think I'm still using my primary bar light ( Gloworm X2, dual emitter lamp ). Not bad for a cheap single XM-L2 emitter torch.

Yes, some flashlights do have a very narrow beam not suitable for the bars. For my helmet I like the Convoy M1. Liked it so much I bought two, one neutral white LED ( for MTB ) the other standard bright white for road use. The M1 has some awesome throw and yet still provides some decent spill. ( Mine are custom setups using XP-L HI emitters and five mode U.I. ) On the road I use the M1 for high-beam duties only. Comes in real handy when flying downhill in areas where deer are known to jump out at you.

Almost forgot to add that I use some nice torch holders I bought off a Chinese website ( now also sold on ebay ). I like the ones that are all metal and use cam-style clamps to hold everything ( both bars and torch ) nice and tight. Been using those types of holders for years and never ever lost a torch. The ones I have also have a little side to side adjustment so that too is handy if you need to aim a little off center. ( I center the swivel on mine and then tape them to keep them from moving ).