To be fair, there is something called "value engineering." Water heaters are a very good example of it.
Henry Ford was reported to wander junkyards, and to take notice of what car parts were out-lasting the entire vehicle. It was his opinion that 'proper design' meant that every component had essentially the same expected life; that additional durability in any component was wasteful.
From the day a water heater is installed, the clock is ticking. It will fill with sediment / scale; the anode will corrode away, the tank will corrode, seals will crack, etc.
So, let's look at the 'fault chain' here.
Say an element goes bad. First of all, a replacement might not accomplish much, if the tank is full of scale. Enough time may have past that the anode is gone, and the tank is rusting away. Worse, the T&P valve may also be obstructed by scale.
In short, remember: We're electricians, not plumbers. Replacing that heater might be the best solution.
For those who haven't seen this before, here is a video of what happens to even a tiny water heater when things go wrong:
http://www.youtube.com/watch?v=GF_Wrm-Ns0I
