You carry a P3AT because it is the smallest and lightest thing available with that level of power. There is no such thing as a free lunch, and the P 3AT will not last as long as a big, heavy gun. However, I don't worry about this: KelTek gives you a lifetime warrenty, and they are really, really good about supporting their products.
Given the price of .380 ammo, it would never be a wise choice for a range gun, but it is very handy when things get ugly. You make your choice and you pay your money.