Hello and welcome to the group. You are not 'required' to use them. However, if you wish to not replace the tubes due to the spokes punching holes in them you will need them. The liners protect the tubes from chaffing against the spoke welds and any rough surfaces.
Another good thing to use when installing the tubes is, if I remember correctly, talcum powder or corn starch, that will help them go into the tire easier and provide some lubricating action.
Mike