I think it is essential, especially if you're not just getting out of the shower. Like JimmyHad I microwave a moist towel-30 seconds in mine. If I skip the hot towel the shave is less enjoyable, I think for me, and the razors.
Somebody told me thick facial hair had the same hardness as equal diameter pure copper. I don't know that it is all that, but, hot towels ease the way for the razor- and therefore your face.
People I know with sensitive skin won't even shave without the towel first. But, like most every aspect of wet shaving- whatever works for you.
There are people who shave with cold water....on purpose! Not me.
If your towel cools too quickly get a thicker one, and try the microwave.
Take care,
Ed
quicknicker