Why MAX232 works without any capacitors?
It's not likely that Max232 is pumping out +/-7.5V or more without the capacitors, more that your terminal accepts the logic level voltage coming out of your pic controller.  

The RS232 spec allows for anything between +3 to +15 and -3 to -15.  If the supply line to the Max232 is 5V then simply providing +/-5V for the max232 is acceptable to your terminal.

Some equipment (sometimes older) require +/-12V and the 7.5V that Max232 would boost to a 5V line would get you there.  As Gustavo mentioned, if you hook it up to a scope you're unlikely to see a sustained +/-12V or more coming out of the max232.