Depends what you are rooting. Many tough common shrubs can be rooted outdoors in ordinary garden soil. e.g. Forsythia, Weigela.

I root with regular potting soil just as often as using only water, or perlite mixed with peat moss.

I even sometimes stick something into the garden, letting it root there.

Some methods need more attention than others, same for the plants.

I haven't used sand yet but I know some YT videos suggest that also.

I use Miracle Gro potting soil and have excellent luck with it. I know most people are down on it. I'm sorry, but it works for me. I've tried the cheaper barky type soil and it hurts my fingers and hands to use it and my plants don't grow as well in it. If I'm going to enjoy repotting and making cuttings I need a soft soil.

'I notice that a lot of videos and comments recommend using
soiless mixtures to get cuttings to root but nobody really states
why...'

A porous, soiless, medium is more successful than soil put into a pot. Soil that has been put into a pot is not the same thing as the very same soil that has been left in the garden. It's structure gets wrecked and drainage is stuffed. Garden soil in pots is far too dense. Roots need oxygen to grow and in a pot of coarse sand or perlite or a mix of both, for example, there is plenty of that.

'does it have to do with the lighter texture making it easy for roots to perforate and restructure?'

My guess is yes, that would help.

Or is it because potting soil is generally less...diseased?

Hmmm... I think it is very beneficial that fresh perlite is free from fungus and such but I suspect that if cuttings become diseased when using soil, then it is due to there being too much water and too little air present. Or over-crowding.

'Two
things about that though: I don't see many who recommend sterilizing
potting soil and I don't see any warning signs regarding diseases.'

I cannot remember whether we steamed our cutting mix or not. I know that we steamed the soil mix that was using for indoor plants as I remember having to wrap black plastic around my boots on the occasions that I climbed up and shovelled the soil onto the bench in the potting shed. My guess is that we probably did steam the cutting mix too.

'For
example when I first researched seed starting i was constantly reminded
that sterile is best because germination failures are often induced by
damping off disease in outside soil.'

Damping off can occur in steamed soil as well. All it takes is sowing the seed too thickly and not enough air movement.

'Is there a disease that is
equivalent to damping off when it comes to producing failure in cuttings
that pushes people into using a potting mix?'

I wouldn't call it a disease, I would just call it a distinct lack of success in rooting. Just one thing, we need to distinguish between cutting mix and potting mix. Potting mix is not as successful as cutting mix. Due to less air in potting mix I think.

'I have a strip of land in my yard that is shaded and gets indirect
sun that I wanted to use for rooting and plant propagation but if I'm
looking at an appreciably higher failure rate for not using containers
with a soulless medium then i will reevaluate using that area'

It sounds like a nice strip to use for plant propagation.