What do all these pipes have in common?
They come from water softeners that are incorrectly and dangerously installed. They could contaminate the drinking water in the home they are in and possibly the whole subdivision.
Water softeners have a pipe coming out of the control unit at the top of the softener (there is usually a lower pipe from the tank overflow).
Water softeners are required by law and by the manufacturers to be installed with a back-flow prevention device, in other words the backwash pipe from the softener must not enter the drain it is connected to, there must be a space between the end of the pipe and the top of the drain. This gap prevents sewage being sucked into the softener (your drinking water) if the drain backs up.
(You could put a 1″ pipe into the 3″ drain and have it sticking up 12″ above the top of the drain, then insert the flex pipe from the softener into the top 3″ of the pipe which would create a back-flow prevention device)