Why do we only have a one year warranty on large national medical devices?

Medical equipment profit margin is partly in sales and partly in after-sales service. Generally if the machine breaks down, the repair cost of a certain part of the repair cost of the original purchase cost of 20 - 60%. Then the maintenance is really profitable. On the other hand, we know that the quality of domestic products is very bad, generally about a year must fail. So the free warranty for a long time, the enterprise's profit is gone. For example, my company's products, the sales price of 3-5 million, a part of the bad, if the repair in 10,000 to 20,000, the cost of 1,000 to 2,000.