why pressure kept on decreasing even in a flow thro uniform cross section pipe&fluid is incompreesible?

Answer 1

Because of the liquid’s non-zero friction with the pipe’s wall, without the difference (drop) in pressure there would be no net force to push the liquid through the pipe. When the flow is blocked, the pressure builds up and equals everywhere along the pipe.

Answer 2

Its called reistance.
Pressure = Force / Area Resistance dissipates/ reduce force causing more pressure drop. It means the pipe dia is smaller for the avaiable flow, therefore more resistance and thus pressure drop.
Molecules of the fluid get a resistance from the pipe surface.
and Resistance is Friction losses. thats is why more viscous looses more pressure.
Thats the simplest I can explain.

Answer 3

the theory of non zero friction is responsible for this .gravity is also responsible from some point of view