you don't want it coming under as you may get slivers under your fingernails.
That's what I reckon too! Strange thing is that Mrs Ozzie has these lovely long manicured nails and yet she still prefers to take the risk of scratching them by wanting the toilet roll to come under!! I don't get it! But then, I never have!!
Cheers, Ozzie (of the perplexed class)