Why don’t we wear tefillin on shabbos and Yom Tov? [duplicate]

Question

I know that we don’t need to wear tefillin on shabbos and Yom Tov because we only need 2 of the 3 signs to be fulfilled (tefillin, bris mila, And shabbos/ Yom Tov), and since we already have a bris mila and it’s shabbos, we don’t need to put on tefillin. (Source needed)

But why don’t we anyway? Just because we don’t need to put tefillin on, doesn’t mean we can’t.

Note: please do not answer that it was never done and therefore it was accepted as Halacha/ it became muktza because it has no use, as it could have been put on when this heter was first made, and through that become a minhag (think ma’ariv).

Please keep in mind that there is an argument in the Gemara whether tefillin is a mitzvas asei shehazman grama or not (kiddushin 35a), so according to one opinion, we should put tefillin on on shabbos, and the minhag (or Halacha) not to was codified since the Gemara.

Answer 1

ערוך השולחן אורח חיים לא א-ב

ומכל מקום כתב רבינו הבית יוסף דבשבת ויום טוב אסור להניח תפילין מפני שהם עצמם אות,ואם מניחים בהם אות אחר היה זלזול לאות שלהם. עד כאן לשונו.
ואין הכוונה לאיסור תורה, אלא איסור משום בזיון שבת ויום טוב. והכי איתא במכילתא סוף פרשה י''ז... רבי יצחק אומר: הואיל ושבת קרויה ''אות'' ותפילין קרויין ''אות'' – לא יתן אות בתוך אות. ...

Aruch Hasulchan Orach-Haim 31:1-2

Anyway, The Beis Yossef wrote that during shabat and festivals, you don't put on teffilin, because they are a "sign", and if you put on another sign, you dishonor them, that his sayings.
And it's not that it Tora prohibition, but it's forbidden to dishonor shabat and festivals.
And in the Mechilta end of p17... R' Itzhak says because shabat is called "sign" and are Teffilin called "sign", don't put a sign within a sign...