A question about house radiators in U.S.A.

[Telecolor 3007]

First of all, I wish you all a Happy New Year, trought all that we've past for some time January 1st.
Well, I've seen that house raidators - like the old cast iron ones in U.S.A. have the faucets (taps) dowm, unlike Europe, where at least for the hot water ones, the main tap is on the upper side. Do radiators from U.S.A. are generally use steam in stad of hot water, so this is why they have thins configuration?