There are only 21 million bitcoins in the world. It is finite. Its supply is limited. If people keep losing their BTC due to loss of wallet seed phrase there will definitely be a decline in supply unless in the case where they can be recovered. For example, a person who dies and didn't tell his family members that he has bitcoins or the recovery phrase. The bitcoins is lost forever and the amount in circulation declines. Although, in my estimation, the effect will be infinitesimal. So, there is nothing to be perturbed about.