I've been checking out previous jam games to understand what you mean by Adventure game, I think I'm starting to understand but I also noticed all the games I checked so far have been Point-and-Click.
Is there a reason for it? Is it required or can normal controls (using arrow keys or joystick) be used?
There's no need for keyboard controls either. As Wiki states about adventure games: "adventure games continue to be popular in the form of visual novels, which make up nearly 70% of PC games released in Japan." So I'm guessing we can do just Visual Novels too? Since that's considered an adventure as well.
There's a fine line between genres and subgenres. Visual novels do count, but only barely. Same with some hidden object games.
It's hard to explain Adventure games to people who haven't played them. Those who have played enough of them tend to get a general feel of what is an adventure game and what isn't.
An example of a game that is mostly a visual novel, but also has elements of adventure games and rpgs is Leviathan: The Last Day of the Decade.
As for why not everyone would be doing visual novels is because there are some of us who joined this jam specifically because it's for making adventure games.
