Let's see... 1.) You need a shit-load of people to play baseball anything like for-real. At minimum 15-20 people for two teams. Pretty tough to do as a kid, unless you're free to roam free all over town to gather a crew, which approximately 0% of kids have license/protection from CPS to do. 2.) You need a big enough area for a baseball diamond, where you don't have to worry about knocking out a window with a foul bal…
Makes me wonder why did this sport ever become so famous. It's like cricket, except there are two large competing sports (football and basketball, even hockey and tennis somehow).
That makes it much harder to improvise a playing field than is the case for baseball, cricket (needs a fairly small area where the ball can bounce off, and having an unpredictable bounce is considered a plus there), or, especially, soccer.
To play soccer, the minimum you need is an old newspaper or old rags that you shape into a ball-like form, something to tie around it to make it keep that shape, and anything that can be placed on the ground to indicate where one should imagine the goal posts to be, such as the coats of four players, marks drawn in the sand, etc.