Hesech Hadaas in Tefillin

HESECH HADAAS IN TEFILLIN

שמות פרק כח, לח וְהָּיָּה עַל -מִּצְחוֹ תָּמִּיד מסכת יומא דף ז/ב הא כתיב תמיד ההוא תמיד שלא יסיח דעתו ממנו כדרבה בר רב הונא דאמר רבה בר רב הונא חייב אדם למשמש בתפיליו בכל שעה ושעה ק"ו מציץ

The Tzitz has only one holy name in it and yet one needs to be consistently aware of wearing it, then even more so for Tefillin which has many holy names in it. Evidently, the main concern is for frivolity when wearing Tefillin, since this ruling is only from the Rabbis, thus, the only concern is in a case of profaning the name of G-d (and not the general lack of awareness, which would be the concern if this concept was of Torah origin).