You, on the other hand, simply restart a new city. Imagine if you just started this game, you have no defenses, and someone just swoops in, attack the two miserable troops that the game puts in by default, and wins? Going by your idea, he takes your entire city, gaining all the benefits that come with it. I like the way LadyMedea puts it, this feature is in place to protect the players who are just starting out, from the stronger players, who probably started earlier and had more time to develop. Although you are forging an empire out of a small village/town/city, this empire is on the Continent Map and those territories conquered grants you further expansions and goods production boosts. Simply because Forge of Empires is a city building game.

To add on to what wizard1001, LadyMedea and Pendragon has said, it is extremely unlikely (1 in a trillion?) that the developers will ever change the game in the direction you are suggesting. For a further explanation on PvP, Towers and medals, do read Pendragon's excellent FAQ: (click me)

These medals can then be used to purchase territory for your own city. You are awarded a certain number of medals by attaining certain positions in those tournaments, which conclues at the end of the week (Sunday). These tournaments are held weekly, and there are different levels for different Ages. When you win a battle, you gain PvP points, which goes to a certain tournament (in Forge of Empires, we call them Towers). You actually do gain territory when you defeat an enemy's city.indirectly.

Forge of empires defending army locked