Lets say a person has accumulated 10,000 BTC over their lifetime...and then...they die. There computer is formatted and either resold or passed on to a relative. Either way the wallet.dat and the private keys are gone.
Thats 10,000 BTC that will never be circulated again.
Someone with $332K USD worth of bitcoins probably should discuss secure storage methods. That person's family will miss those coins. Sad.
It that occurred only 21,000 or so times. That would the whole of BitCoins in circulation would it not ?
Incredibly unlikely, for sure, that there would be 21,000 people each with $332K USD worth of bitcoins and all are completely clueless and careless.
But, for the sake of argument, let's say there are 20,999 people with $332K USD worth of bitcoins who are completely clueless and careless, and
just one remaining thinking individual who has proper storage of the 10,000 BTC. These happen to be the last remaining bitcoins that exist since everyone else lost theirs.
Well, guess what. .. a single bitcoin is equal to 100,000,000 Satoshis, so that means there are still 1,000,000,000,000 Satoshis for circulation, or nearly 140 Satoshis per man, woman and child on the planet today.
Now, of course, let's assume the valuation is the same, and that person with 10,000 BTC would be sitting pretty, because at $342 million worth, the BTC/USD of each of the 10,000 BTCs would be worth $34,200. Score!
tl;dr: Lost coins hurts the party that lost the coins. Without those coins the value of the remaining coins will likely increase roughly at the same proportion.