Containers using default bridge network cannot communicate?

Hi, i’ve created 2 simple containers -
the first one - is just a simple python web service that echos back.
the second is just a simple bash with curl.

i can freely ping between the containers, but i cannot access the web service from the bash container.
i can access the web service from the localhost itself.

when i had run them with a custom network (–net flag) - they were able to communicate well.

I wanted to ask why is this happening with the default bridge network?