Why stock watchface can show seconds all the time and custom watchfaces can't?

Look man , always you will find this people who are saying " why you want to have moving second hand " 

Will the answer is that it is very beautiful and show that you are having a real watch , it is cool , among other benefits for people who want it in thire work , and before all that , if we have it in the original watch faces why we don't have if on the other watch faces ?? , Sure some one will come and say " it is draining the battery " well , no it is not , because it is there in the original watch faces .

Renumber that most ot time watch will be on the AOD 

Sure some one will come and say " it is draining the battery " well , no it is not , because it is there in the original watch faces .

As I said years ago, the native watch faces are written directly in the watch firmware. They are optimized to minimize power usage, and they run directly on the device CPU. A ConnectIQ watch face is non-optimized code that runs on top of a virtual machine that runs on top of the watch firmware. These additional layers provide some advantages and disadvantages; increased power usage is a big one.

Last time I looked into this, a ConnectIQ watch face consumes more battery power than any of the built-in watch faces. The overhead of the ConnectIQ Virtual Machine is non-zero and the built-in watch faces are *very* power aware.

As jim_m_58 pointed out, about two years after this thread was started functionality for displaying seconds was added to the API. It was done in a way that restricts what you can do, all to avoid draining the battery.