Why some WWII fighters still have fabric/wood control surfaces?
A metal control surface can also sustain some small arms fire without disintegrating -- aircraft with metal rudders and elevators used to routinely come home with bullet holes in those surfaces.

The real reasons wood and fabric surfaces might have been preferred (though they weren't always; several designs had all-metal control surfaces) are the classic reasons for everything in aviation: cost and weight.  In the late 1930s, when many of the aircraft used in WWII were designed, it was still possible to make a wood and fabric structure, especially a control surface (as opposed to a wing), that would give the needed performance and strength and come in lighter than an all metal one, and frequently at lower cost in volume manufacturing.

As performance specifications continually crept up (higher speed, higher loading, more vibration from a larger engine, etc.), metal surfaces gained the advantage.  They could ultimately be stronger than wood and fabric, hold their surface shape over a broader speed and pressure envelope, and as noted, wouldn't disintegrate if they took a few bullets -- in fact, they were usually more durable than wood and fabric, because metal is less prone to tears and splintering.