Lost bitcoin is not gonna be a matter in the economy. If the lost bitcoin is considered it will give a increase in price. Because the lost will considered as a crypt in circulation.
In terms of usability probably it doesn`t affect too much, But in economic question would be analyzed more carefully.
Suppose for example that someone decides to buy all BTC existing and pay all marketcap entire for it , how many should receive? Without going any further the mega-buyer it would have to know how many actually exist in circulation and have not been lost to ensure that all are delivered to him/she. This is just a hypothetical case belongs rather to the theoretical field. It may sound farfetched now but it could be the case that this can become real some day.