There are rare cases when an appliance (or any other product) will fail long before the average lifespan for that product has lapsed. This is one of those cases.
The manufacturer's warranty is paid for by the manufacturer. In this case, the manufacturer is Whirlpool. Whirlpool pays Sears to do the service on your dishwasher during the manufacturer's warranty period (one year). After that, Sears is paid by the owner of the product for service. This is not a new thing, nor is it exclusive to Sears.
Not to sound callous, but I'm quite sure that when you purchased your dishwasher, the sales associate offered you our Master Protection Agreement, and explained how you would receive annual maintenance checks and complete coverage for any and all repairs due to defects or normal wear and tear.
I am assuming, because you've posted expecting Sears to fix for free what it has no obligation to fix for free, that you declined the protection agreement. We offer it because, while the vast, vast majority of appliances don't have problems early in their lives, or within 5 years, even, that doesn't mean that you won't get the one that does. It's an easy way to safeguard yourself against unexpected repair costs.
I am assuming that you told the associate some variation of "we don't want it, we'll take our chances" when offered the protection agreement (a mere $30-45/year). When we gamble, we might win, but we also might not. That's the chance we take.
While your dishwasher certainly isn't having what would be deemed a normal run, that does not create an obligation to fix it at no charge and eat that cost.
Would your dealership fix a car that was beyond the manufacturer's warranty for free?
Or, to put it in a different light, how would Sears look to customers if they knew that they could get for free what they should rightly be paying for? Would Sears be deemed a savior or a sucker? They'd be a savior to you for the moment, but from then on, you'd know that you could get free stuff from Sears if you just try hard enough. Then Sears would be a sucker.
To be perfectly frank, Sears is a business, not a charity, and while losing money on a single customer might be justifiable as good business, losing money on every single customer is bad business. Sears would have to give free out-of-warranty service to everyone if it gave it to anyone (it is, to put it crudely, like feeding strays). If you like Sears, and want to see Sears succeed and continue to be a great place to shop, asking it to give away hundreds of dollars of merchandise and service to everyone who asks for it is directly counter to Sears being able to survive.
And, to be fair, you claim you've always bought Kenmore. Presumably they did not give you any problems, so clearly it's not that quality is an issue overall, it's just that you got a dud that took a while to manifest its problem.
With all that said, rather than posing your question as "I'm important to you, so give me stuff," I suggest you call your local Sears store, explain what the dishwasher is doing, and mention how young the dishwasher is. If you avoid making it sound like you're demanding free service, they may be inclined to call our service branch and relay your story, and the service branch would call you to see what can be done, if anything.
You may not be aware of it, but you're using vinegar when you should be using honey. Honey is REALLY attractive, and vinegar is REALLY repulsive. The right approach can make all the difference.