Beneficial bacteria are aerobic, and live on surfaces as biofilm.
If you don't occasionally get rid of the gunk the biofilm can become covered, and the area can become anoxic (even anaerobic).
One of the reasons fluidized beds work so well, is with motion, the gunk doesn't get a chance to build up and become anoxic. Old less robust bacteria are washed away leaving room for newer healthier biofilm.
Shaking off gunk in some water change water regularely helps biomedia stay aerobic and the bacteria robust.
Never cleaning biomedia, (such as is normally done routines in canister filters) defects its purpose.
Media such as lava rock doesn't clog any faster than any other media, unless that other media is fluidized.
Below one of my fluidized creator chambers, its about 4ft tall, and 8" in diameter.

It uses aragonite sand as media, which also buffers pH beside the beneficial component

The flow empties into a 50 barrel as a sump.