Why do Catholics put ashes on their heads

The act of putting on ashes symbolizes fragility and mortality, and the need to be redeemed by the mercy of God. Far from being a merely external act, the Church has retained the use of ashes to symbolize that attitude of internal penance to which all the baptized are called during Lent. The faithful who come to receive ashes should be assisted in perceiving the implicit internal significance of this act, which disposes them towards conversion and renewed Easter commitment.
--- Directory for Popular Piety http://www.vatican.va/roman_curia/congregations/ccdds/documents/rc_con_ccdds_doc_20020513_vers-direttorio_en.html

I wonder why some will be forever searching for, or fabricating new rituals and practices. The Church already has them, She is LOADED with them!
Tolle, lege!
(And now, I don't mean "pick up and read the latest make-em-up-as-you-go-along handbook from LTP." We as a society have forgotten the difference between primary and secondary sources. Our middle school teachers seem never to have taught us, when we were learning how to research for papers.)
I often hear the idea that we can infuse the Rites of the Church with "meaning" by our interpolations and deformations -- such hubris!
As if the meaning weren't innate! and such meaning that our puny attempts at adding relevance end up mocking if not the Rites, than mocking our selves.