Muslims use worry beads for a similar reason, to chant repetitive rote phrases. Where in the Bible does it say to use a device in order to talk to God? Why would one need such a device? Neither Jesus, His disciples nor His mother had a rosary.
Yes, and Jews use prayer beads, which is perhaps the origin of Christian rosaries and Muslims worry beads.
But so what? Muslims, Jews, Hindus and Buddhists all pray. Should Christians stop praying because non-Christians also pray? Should Christians stop using beads because non-Christians also use beads?
Sharing similar tools with non-Christian religions doesn't invalidate those tools when applied to Christian ends.