As Joe mentions, the appeals success rate is pretty high, however this does differ dramatically between countries.
Although it won't be 'written policy' by the embassy, a pattern has emerged over the years. If they have any doubt they'll deny a visa, the majority of folk trying to 'fiddle' a way into Britain would then tend to fall off the radar. Those who are honest and just messed up with the first application will generally appeal or go the Spouse route.
This is a simple but effective way of weeding out some of the crap applications, as you can bet that of the 100% refusals, they do not have 100% appeals.
