Uncoated lens are prone to scratches. Coated lenses added a hard layer that protected the glass.
I think that's why uncoated lenses get the reputation for being "soft." Optical glass can't really be soft. Otherwise, it would bend and melt if left in a hot car.
The thing with uncoated lenses is how they were handled over the years. Aggressive cleaning has caused many to have "surface cleaning" marks, which are just minute scratches. I've had several lenses that have been damaged by this.
There also is a natural process called "blooming," which affects some uncoated lenses. The result is that it can help to reduce intralens reflections, although it doesn't protect the lens like anti-reflective coating does.
I have always wondered what would be entailed in coating lenses at home. Seems like a handy fellow could do some sort of coating.
I think it's doable, if someone wants to devote the time and effort. I want to try it, I've had good success silvering a telescope mirror... only took two tries.
Lenses you don't value to practice on.;)
Oh yes, a lot of skill and time to practice.
Just seems like something I could do. Time and again in my life I've undertaken service, repair, restoration projects on, that I had previously never even seen done; and ended up with expert-quality results. It's all in the mentality I suppose. I've always held a standard for myself that there's 2 grades of work--perfect or knucklehead.
Just another dumb idea I'll never have the money to fool with.