These are one of the top features that i like when talking about the new technologies. Their purpose is to reduce the number of the circulating coins/tokens which means that the initial circulating supply might be so high which influences on the price and might causes a growth decrease. Burning some sort of amount when a transaction is being confirmed will bring more investors because a lower circulating supply means a higher price in the future which is just going to make investor's hype grow day by day. It's good, that rule might not be always valid but that's the deal.
I agree with your point that initial circulating supply of coin may be so high that may lead to decrease in value. Burning this massive supply to create scarcity and that too within short span may achieve the goal i.e. increase in price with less supply.
BOOM started with 1 Billion coins and now the circulating supply is 782 million coins. This means there are people who are using this coin and that's why over 200 million coins have been burned so far. In coming 3 to 4 years there circulating supply will decrease to significant level.