Beauty is in the Eyes of the Beholder

Ever heard that phrase before? Well, it would seem that the following idea would strongly support this logic:
From the passuk "זה א-לי ואנוהו - this is my G-d and I will beautify Him," the Gemara learns the obligation to "beautify the mitzvos we perform in front of Him." (שבת קלג, ב)
Now, with regards to things that will be openly displayed to the public, all agree that beautification is required. Thus, a Sefer Torah which is read publicly and held high for all to see, must be of high aesthetical value. To ensure a clean and straight handwriting, lines are scratched on the parchment, called "sirtut," to guide the scribe as he applies ink to parchment.
Tefillin do not have the "sirtut" obligation. Why? Explains Tosfos and the Rambam that the scrolls are rolled up and obscured from the public (and private) view, which render the need for beauty unnecessary. Or, in their words "for beauty is not 'applicable' by them."
תוס' מנחות לב, ב ד"ה הא