Building a stilltent on open sand does sound dangerous. It's worth noting that the tents we see being used in Dune are mainly sited on rocky outcrops, presumably so that the Worms will avoid them.
Paul stared out the transparent end of the stilltent at the
moonshadowed rocks that ringed this place where Idaho had hidden them.
Night still covered the stilltent within its rock-enclosed hideaway.
His mother’s grief could still be heard.
“I’ll put up the tent,” he said. “Better slip off that robe and shake it out.” He turned away, taking the pack.
Jessica nodded, suddenly too tired to answer.
“There’s anchor holes in the rock,” Paul said. “Someone’s tented here before.”
Where tents are used on the open erg, it's on soft sand sheltered by surrounding dunes, where presumably their sounds will be muffled.
The reassurance gave him a new hold on his world. Bits of solid
reality began to dip through the dream state into his awareness. He
knew suddenly that he was in a hiereg, a desert camp. Chani had
planted their stilltent on flour-sand for its softness.