That's a scaling issue. Communes work well up to about 100 people. Today's larger kibbutz is more like a company with worker housing. "Differential pay was introduced into the kibbutz structure; management has become increasingly professionalized; and the community and business structures have been separated"[1]
Hence the "ideologically pure" caveat; there is a fascinating subset of kibbutzim which make enough money to essentially function as post-scarcity economies (making things like Humvee armor add-ons for the Americans, or high-end vending machines for e.g. movie rentals). Those have been able to stay ideologically pure by being more effective players in a capitalist system [1], and once they reach that state they are able to maintain it through social forces.
[1] which of course creates some serious cognitive dissonance for all involved
[1] http://www.jewishvirtuallibrary.org/history-and-overview-of-...