Once you've bought, then it's just your bad luck, but until the day you've completed, it would generally be far less damaging to the seller to lose the sale than for the buyer to have suddenly lost his income and at the same time be required to pay out tens of thousands of pounds in compensation. Sellers frequently have more than one buyer interested and may lose a small amount, the buyer could lose their family home, which often leads to relationship breakups and illness. Like many things in life, putting a law in place to stop one thing can have severe unintended consequences for innocent people and it would probably be more practical for the seller to take out insurance for the smaller loss, with the costs being added to the house price.
SteveW