In the typical case of a smooth object (like a block) sliding down a ramp, once the gravitational force down the ramp exceeds the level of static friction between the ramp and the block, it begins to accelerate down the ramp. The acceleration is mostly constant until the block gets to the bottom of the ramp (or incurs some kind of parasitic drag from the air).
A sticky item, such as a block made out of rubber, slides slowly down the ramp but doesn't accelerate. It appears to quickly hit its max velocity and then maintains that velocity until it gets to the bottom.
Why is that the case?