Absolutely there are coins which will be lost, forgotten, destroyed and abandoned.
Because we are dealing with a digital entity a number of things can happen
particularly human related.

Forgetting wallet passwords and sending coins to different token addresses are the
two most frequent occurances for unusable coins and decreasing coin amounts.
Other factors like discarding old hardware while forgetting there is crypto stored on
it has happened in the past particularly when BTC was valued at a couple of $'s

Hardware failure is another one but not a big factor but does happen.

Abandonment is another possibility. Personally I have some crypto on exchanges with
nominal amounts still in wallets and it is not economically viable to retrieve them
and possibly will never be possible because of the fees involved but all these small
values amount to something.