For tolerably obvious logistical reasons, almost all the information presidents get has to be reading (and, one hopes, thinking) and listening to people who come to where the president is. If they can't mostly learn without being on site, we have a problem. (A chorus repeats the last bit.)
Not only that, but much of what a president sees on a visit is going to be dressed up.
Note that there are legitimate reasons for presidents to travel-- negotiation makes sense, and so does showing that they care. But is there any evidence that they actually find facts?