People are willing to support institutions that offer them significant benefits at fair prices.
Some large congregations can make large numbers of people feel welcome, but it is very tough.
Steve also made a telling point concerning his perception that Orthodox congregations are better at this than Conservative or Reform. This is not necessarily true, but they do have a great advantage. I believe the decision of conservative to permit riding to services was major mistake, not from the point of halakah, but from the point of community. Once you say that your choice of housing neighborhood is more important than your choice of Jewish community, many things follow. Getting kids to Hebrew or Sunday School is a schlep.