Why do we have dogs? I do not know. They cost money. They eat ... a lot. They smell. They shed. They really provide no tangible benefit on the surface. But spend those last moments with your dog before he slips the fetters of this world, where he ceases to exist in your moment, and you find exactly why.
He taught me a lot in his short years here on Earth: When you are young, make lots of friends, but when you grow up, stick with the ones you know love you back; when you do love, do so unconditionally; when your spidey sense says something is wrong, it probably is; play hard, but sleep harder; never grow up, just grow older and slower; never care enough to discover conclusively the things you don't like; enjoy everything in life (except nail trimmings and ear cleanings, which are debatable); and, finally, when someone is having a bad day, licking their face instantly makes them forget what was so bad.