I wonder if this culture arises out of necessity. Many conferences claim to not have a set quota of papers they accept, but in practice there is a limitation to how many presentations can be accommodated given the physical and temporal limitations of the venue. The quota may grow slightly over time, either by shrinking the time allotted to every presentation (ICFP is really squeezing it these years, for example) or adding parallel tracks, but there are ultimately fairly hard physical restrictions. This inevitably limits how many submissions can be accepted, which also creates an otherwise unnecessary air of competition, even between otherwise unrelated papers.

Journals don't have this restriction; you can always put out more volumes. I suppose I enjoy conferences as much as any CS practitioner, but it does not strike me as a sustainable or scalable publication method.