Why would I invest 500 BTC at 0.25% when I can just invest 125BTC at 1% then and not have the CP risk for the othet 375 BTC?
Because you would get less variance.
Suppose a whale bets max bet and wins 20 times. If you invest 500 BTC at 0.25%, you'll still have 95% of your bankroll left:
>>> a=500
>>> for i in range(20): a *= (1-0.0025); print "%.2f" % (a*100/500,),
99.75 99.50 99.25 99.00 98.76 98.51 98.26 98.02 97.77 97.53 97.28 97.04 96.80 96.56 96.31 96.07 95.83 95.59 95.36 95.12
But if you invest 125 BTC at 1%, you'll have only 82% of it left:
>>> a=125
>>> for i in range(20): a *= (1-0.0100); print "%.2f" % (a*100/125,),
99.00 98.01 97.03 96.06 95.10 94.15 93.21 92.27 91.35 90.44 89.53 88.64 87.75 86.87 86.01 85.15 84.29 83.45 82.62 81.79
Your risk of ruin is much greater if you invest at 1% than if you invest at 0.25%.