Skin streatching( do'/don't?)

I do wonder, if stretching is important when using a straight why do some folks not do it when using a DE? I do a little bit of it in places but not during the whole shave.

To me it's a no brainer. You maximize efficiency and minimize risk of nicks by giving the blade a flatter more stable surface on which to glide. I laugh in disbelief at guys who say it's their tough old barbed wire whiskers that necessitate 3+ passes but don't abide by this most basic technique.

I do wonder, if stretching is important when using a straight why do some folks not do it when using a DE? I do a little bit of it in places but not during the whole shave.

I have checked out his videos they're very informative, I'll be working on those techniques (probably won't be trying the Gillette slide as I think that's what I did with my dad's razor when I was a kid, scared me from De razors, I cut myself mutiply times, kinda like that haha ouch!) And I did see a couple of videos from your link that I hadn't, the stretch from the waist
and the bullfrog will be giving a shot.

@ 73, shaving since approximately 1963 or 4, I can't honestly remember when I began stretching skin. I shaved with DEs until the mid 80s when I became interested in straight razors. An old barber in NJ taught me to hone, and to stretch skin when shaving with straights. His honing lessons weren't adequate and I ended up giving up straights a short time later until 2007. I think I continued to stretch skin when shaving with DEs subsequent to that interlude with straights in the 80s ... before I went back to straights in 07. 

Returning to straights in 07 I learned to hone well enough to maintain my own, and even to help others out once in awhile. I shaved with straights almost exclusively for over a decade, giving up on them only in the past couple of years. Stretching skin is an absolute must in my shaving routine, and whether you're using one tool or another, AFAIC you will have a better shave stretching skin than not. IMHO. 

Dragonsbeard

While collagen gives structure to the skin, elastin allows it to stretch. Skin that is stretched beyond the normal level is known as hyperelastic skin. This occurs when there is a rapid increase in collagen or elastin production becomes low, causing the skin to lose its capacity for elasticity. It is a big problem for adults that are over forty years. I was always having low elasticity of my skin, so it is why I have made a facelift at visageclinic.com. It constantly made my skin look young and giving it elasticity.