it's funny and strange coz we can refuel the plane in the air by add fuel quantity in the CDU. I think u have to fix this instead no need a fuel planner

This is the same as saying "It's funny and strange that we can right click the clock and time warp at 4x speed. I think u have to fix this instead no need a time to fly "

 

This simulation isn't real life. Some people want to start a flight "in the air" for various reasons (Practice approach, jump into the sky and catch a landing on a vatsim flyin, whatever) so being unable to adjust fuel airborne (up OR down, say from the starting panel state to a landing weight in 2 seconds) takes away functionality of the SIMULATOR so that some dweeb can feel smug about being teh real life trollolol.

 

Just like the time compression, if you don't want to use it, don't.

it's funny and strange coz we can refuel the plane in the air by add fuel quantity in the CDU. I think u have to fix this instead no need a fuel planner

 

It's not really strange.  If you don't want to fuel the aircraft in mid air, then don't do it.  You can avoid fueling in the air just like you can avoid using time compression if you don't want to.