In another life I wanted to pursue a career in art. Having taken numerous art classes it was ingrained in me to always sign your work. Not only for provinance but simply because you took the time to create the piece of art, the very least you should do is sign it and date it. I feel the same about my quilts but I do have a few that I have made and use around the house that are not labeled. Many quilters sign and date their quilts in the quilting itself. Diane Gaudynski signs her quilts with the quilting.
My view is you never know what may happen in your lifetime... You may become famous, or God forbid you may pass away unexpectedly, who knows. Having your quilts signed and dated in some way, either with a label or incorporated into the quilting, means a lot more to the people who have them if either occurs. It is not a historic provenance so much as it means something to the recipients. A loving reminder of the quilted gift. That's my view on it. If the quilt does become an heirloom, whether that was the makers intent or not, signing or labeling means a world of difference to the people in possession of the quilt. I personally think it is sad that makers do not sign or label their quilt in any way. It is almost as though you are not proud enough of your work to take credit for it, even if your intent was for it to be used up and loved to death in your lifetime. JMHO.