I believe it's a matter of MISINFORMATION. Satan works constantly to misinform Christians in attempts to lead them astray. They simply don't know that baptizing someone won't save them. Thus, they act outta good intent, not maliciously or deliberately sinfully.
All spiritual deception originates with Satan. The source of misinformation is found in the doctrines of the denominations with which the parents identify. The reason they don't know that baptizing someone won't save them is because they have been taught it either saves the child or enables them to be saved.
A child of God should grow in the knowledge of his Savior and not continue in ignorance of spiritual practices. The Holy Spirit will guide them to the truth.
2Pe 3:17 KJV - Ye therefore, beloved, seeing ye know [these things] before, beware lest ye also, being led away with the error of the wicked, fall from your own stedfastness.
2Pe 3:18 KJV - But grow in grace, and [in] the knowledge of our Lord and Saviour Jesus Christ. To him [be] glory both now and for ever. Amen.