>>1466945That's because you weren't tightly circumcised, and therefore can still move the remaining skin of your penis.
Not every cut guy is like this; a fair number of guys have tight circumcisions, meaning that the remaining skin and mucosa of their penis is fully immobilized.
Circumcisions like this used to be specifically advocated because they made it much harder to masturbate; not only was a lot of erogenous tissue removed, but the penis would be straitjacketed in its own remaining skin.
>In all cases [of masturbation] circumcision is undoubtedly the physicians' closest friend and ally...To obtain the best results one must cut away enough skin and mucous membrane to rather put it on the stretch when erections come later. There must be no play in the skin after the wound has thoroughly healed, but it must fit tightly over the penis, for should there be any play the patient will be found to readily resume his practice, not begrudging the time and extra energy required to produce the orgasm. It is true, however, that the longer it takes to have an orgasm, the less frequently it will be attempted, consequently the greater the benefit gained...The younger the patient operated upon the more pronounced the benefit, though occasionally we find patients who were circumcised before puberty that require a resection of the skin, as it has grown loose and pliant after that epoch.E. J. Spratling. Masturbation in the Adult. Medical Record 1895;24:442-443.
Even today some parents still request "tight" circumcisions because they think masturbation is wrong, or because they think it looks better and don't really care about the distorted function. Some guys were cut so tight that their erections hurt and if they try to masturbate dry their skin rips apart and bleeds.
https://www.youtube.com/watch?v=5DRsJXJop5I 
