The ease of uniting hand and cock does keep frustration at bay, but one's thoughts and the images that come to mind in these solo sessions tell us that the brain is still the greatest organ for sexual pleasure. Deep in thought one can create the setting in which the visceral resources are brought into full play.
Merely seeing a sexually attractive person and endowing that fully-clothed person with whatever is needed to bring the "stirring" to the point of high excitement, I know that I will have to hit the bathroom to take care of that delightful lubrication, which my ample foreskin usually contains long enough for me to get to a stall. There I can use it for a delightful wank. It all makes me glad both for the "animal urges" and for the creative thought processes which enhance such moments.
And, for the truly sensuous man, the solo experiences have the happy capacity of preparing one for the anticipated shared joys of sex with one's beloved partner.