Has anyone walked on a planet other than the moon? If not why?
Well, billions and billions of people have walked on the planet called “Earth”
Ba-Dum BOOM!
Thanks, I’ll be here all night…
Other than Earth and its natural satellite, no human has ever set foot on any other world. (We are of course free to speculate about whether “anyone” includes possible extraterrestrials.)
As to “why”: crossing interplanetary space is difficult; it takes months to years to do so, and thus far no one has found a sufficiently compelling reason to develop the technology to allow humans to do so. Getting people out there is a lot harder than getting robots (people need food and water and air, and have this tendency to want to come back when the mission is over); so far, robots have been able to accomplish all the objectives which the spacefaring nations have wanted to accomplish on or around other planets. (And thus far, deep space exploration is still a game played by nations or groups of nations, and not by private individuals or non-governmental entitites.)
A popular nutcase called George Adamski claimed to have visited Venus. He caused quite a stir in the 1960s.
I walked on Saturn once. But that was back in the 80’s, after a dose of microdot.
There was this great meteorite collector way back who went around to schools displaying his collection. I got to help him set up and pack. Great fun. One of his prized meteorites was metallic one shaped like a half deflated ball. It was put on the floor and with a sign telling you that you could step on another world. (Wish I could remember his name. No luck Googling.)
As far as the other planets:
Mercury. Too hot on the sunny side. Might be cool enough to land on the night side and hang out for a few weeks.
Venus. The atmosphere is quite hostile. No hope of a walk with current technology.
Jupiter, Saturn, Uranus and Neptune. No surface.
That leaves Mars and Pluto. Mars is close enough that current tech. could lead to a walk. The main issue is $. Pluto is so far that it would be one hell of a long mission and who wants to walk on a planetoid?
Note that the Moon is not normally considered a planet, although some do argue that we are a double planet system.
Another reason is the commute is a btch. 
Superman and Alf. :o [sup]Seems like someone else, but my memory is slipping.[/sup]
OH, yeah. E.T.