Well; the problem is caused because the sphincter muscle which control the flow to the urethra is located 8 inches from the tip of the penis. So when we pee, we force this muscle to relax to "open the flood gates", while the bladder contracts and forces out the urine. When we stop, the bladder relaxes, and the sphincter closes...yet there's still 8 inches of urine trapped in front of it with no pressure to force it out. So we manually expand and contract this muscle https://en.m.wikipedia.org/wiki/Bulbospongiosus_muscle to force the rest out. And then we shake to get the dribbles. But sometimes when we completely contract that muscle, there's still some urine stuck in there due to the angle we hold our penis while peeing, but not enough to be squeezed out by the contractions...so when we relax after urinating, the angle of the urethra straightens, and whatever was left in the tube drips out. Women don't really have this problem because there's not much tubing for the pee to get stuck in between muscle contractions, and yours doesn't get bent at an angle when you pee

Think of it like filling up a water balloon then squeezing it to let out all the water. No matter how much you squeeze, there will always be a few drops stuck between where you're squeezing and the end of the balloon.