One little-known side effect of nursing a baby is vaginal dryness. Has something to do with the hormones, I think. With my wife, sex during that period would have been near-impossible but for my foreskin serving like a bearing.
Plus, to enter her, I would bunch up my foreskin like puckering for a kiss, press it against her labia, and keep it tight there like a lip-lock while my glans slipped into and out of her, back into the foreskin each time. This spread her precious lube out gradually, wasting none of it, and allowed me to get into her with just a few strokes.
I don't know if many people realize how fast vaginal moisture dries up when exposed to air.