TBH that is just a case of bad luck and RNG, for most people that does not happen. Hell if you had two accounts running you would have not had it happen for the other one. You are quite special in one sense that the chance of what happened to you statistically, is less than the chance to have drawn a 6* in all those pulls.
From my experience at least 50% of 10+1 pulls have netted at least 1 5*, I say at least because personally I have not had all that many salt pulls so my actual % of at least 1 5* is closer to 75% of 10+1 pulls. Having said that I do tend to wait and make those 10+1 on the day a new event is released and I have found more luck that way. Statistically speaking you should get a 5* every 20 girls you pull, RNG tends to inflate that a bit sometimes tho.