I'm saving bitcoin for retirement and will not move my coins for 20 years. You've just stolen my money.
I've timelocked some bitcoin for 21 years as an inheritance for a new family member. You've just stolen my money.
I'm a political dissident who has been detained without trial by a dictatorship for 15 years. You've just stolen my money.
I've been sent to jail for non-violent victimless crimes for 10 years. You've just stolen my money.
I've been working in another country for 10 years with some wallets safely stored at my parent's/other family member's house which I have not accessed. You've just stolen my money.
There are a hundred other reasons someone might not move their coins for 10 years. That does not give you the right to steal them.

And that's without even touching on the crazy idea of implementing a system which allows coins to be moved with providing a signature.