[Johnjonjoan]

I'm not sure how right this is but I was told it's to do with time dilation. If you're moving close to the speed of light, stuff that isn't is experiencing way more time than you. As light isn't affected by time dilation it's still traveling at the same speed but now has much longer to do so. So from your perspective the speed of light seems to be 190% not because it's traveling faster than C but because it's traveling more C seconds per your second when your time is dilated.

Edit: on further reading perhaps I haven't even addressed your question...

If I had to hazard a guess I would say it's to do with light having no mass. Once it's emitted it's no longer in your frame of reference so your supposed speed is irrelevant to it.