I suppose they thought scars weren't important... but I actually liked them very much. Not only because they glow, but also because they are a special mark on Shepard... something that makes her/him remember how she/he died and came back to life two years later :\
That's exactly what I think about the scars, they are a part of Shepard now It's just a shame you have to be mean to keep them without mods /: oh well, maybe one day right?
Yeah, though mods are quite cool. In ME2 I gave one of my Shepards blue glowing eyes (like TIM). It is possible in ME3 as well, but it's more complicated. Oh! I just remembered! I think in ME3 you can keep the scars, but only if your Shepard was a renegade in ME2...