In "Monkey's Paw", what is probably troubling the Sergeant-Major about the White family's lack of concern towards the paw?

The Sergeant Major gives the Whites' plenty of warning about the dire consequences of the monkey's paw.  What is troubling for him is that they do not seem deterred by the warnings.

Sergeant Major Morris knows that something terrible is going to happen to the White family, but the Whites' are very casual about trying out the paw, in fact they don't believe the Sergeant Major's warnings.  To them, it is almost a joke, that the monkey's paw has any power at all.  

Mr. White believes, that the other two owners, the first, whose last wish was for death, and the Sergeant Major, did not use the monkey's paw responsibly.  He imagines that they made outlandish wishes and that is why the first owner wished for death, and why Sergeant Major Morris is nervous and keeps drinking to soothe himself.

"The Sergeant-Major tells them that a fakir has put a spell on the paw "to show that fate ruled people's lives," Those who tamper with fate "did so to their sorrow." But Herbert coaxes his father to wish for something modest, like 200 pounds."

Nonetheless, Mr. White makes the wish for 200 pounds and when nothing happens right away, he thinks that the whole thing is a hoax.