cos then the weight saving is lost,
CDS is a "nicer" material than blue band, T45 is a nicer material than CDS, however nice they are & strong they are on paper it doesnt account for the fact we do things to the tube that the manufacturers didnt design the tube to do,
going racing & having an internal cage then IMHO CDS/t45 is as good as it gets, for an external cage then unless you use the thick wall cds you are no worse of using blueband as its much more resiliant to knocks & impacts,
i know of 2 truck cab cages made from T45 that have had to have major repairs to them,
1 vehicle was rolled & the other was lent on a tree hard, if they were blueband or thickwall cds then i very much doubt that they would have needed the repairs,
i am also aware of a cds spaceframe that had a lie down at the decider & resulted in bent sidebars & the tube torn away from the welds,
my own spaceframe which is built from blueband has been over couple o times now & have hit trees "hard" & as yet there isnt any damage or dinks & dents to the tube,
its all swings & roundabouts but to say that blueband shouldnt be used & will get you killed is utter rubbish,