Actually, that’s not true, but your point is well taken.
Certainly in recent memory, maybe Nixon left worth less than when he was elected.
Carter, I have no idea and the same with Ford though I don’t think Gerald Ford was particularly wealthy anyway.
Reagan didn’t profit while in office but was able to do very well after leaving.
Obama and Clinton made out like thieves in a bank vault.
I have no idea about the first Bushes.
The second Bush made money hand over fist just before he became governor and sold his stake in the Texas Ranger’s baseball team.
Trump stands to lose a lot of money as President and that is rare.