I think there is a little residual fear of Lipos from when they were very new and much more unpredictable.
Some new Lipos can be charged at at 6C and above now (with new L-ion going miles higher than that)
So if using a good balance charger and staying within the limits I dont see the need for a bag.
...however..... I have seen things done at a race event that you wouldnt dream of doing at home. Massive C values being pumped into already warm batteries coming straight out of a race. And if you cant find the balancing leads, dont balance it and whack the charge in!!
Its at those times that I cant help but feel a charge bag would be a good idea - especially if Im in the adjoining pit area (and downwind!!)
Let the Icelandic ash cloud be a warning to us all
