Earlier quoted context omitted.
This disgusts me. The president should not have the power to free anyone from prison. If the laws are broken then (attempt to) change those, but otherwise you’re just saying “yeah, you’re guilty, but I like you so you don’t need to serve your time like everyone else”.
I believe it was originally designed to be a safety valve in the system. A person can be found guilty because the laws are blind, but if a (loud) majority of the population thinks it was a misjustice, the president can fix the situation. I don't think any of the founding fathers foresaw presidents using their power to pardon their friends. The whole system is extremely vulnerable to an insider attack - very few tools…
Interestingly, this pattern repeats itself; countries which became independent from Britain later on often have a far less powerful president, with similar powers to when _they_ left. The president of Ireland, for instance, is non-executive, doesn't have a veto, and can't commute sentences... much like the British monarch when Ireland became independent.
As it stands, it's an anachronism that only survives because it's _really_ difficult to change the US constitution, I suspect.