[rsynnott]

Well, realistically, it was just copied off powers that the British monarch had at the time. Lots of the oddities of the US presidential institution can be traced back to that.

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.