Interestingly, the expense of Little League is self-imposed.
Many travel leagues require kids to also join a “house league” for the exact reason you cite. However, that creates an insane over commitment for the kids (and parents!!) and the travel players usually have poor attendance for their Little League teams, which is an ENORMOUS factor in their reduction and a big cause of many teams folding. No one wants to pay for Little League only to lose half your games due to forfeit.
Even if the travel leagues abandoned that rule (as some have), the depletion of Little League teams at the expense of travel ball strongly indicates there are more kids serious about baseball and fewer in pursuit of a casual summertime activity.
Probably worth noting - Little League itself isn’t really the same casual baseball we had as kids. It’s also a big, big deal now. And gone so far as to have the LLWS televised nationally with multiple countries participating. Unlike MLB, when Little League has a World Series, they actually invite the whole world…