You answered your question in the asking of it. Because they are careerist. They are in competition of the Christians out there. In their mind great if i can convince some to BECOME christian (what a novel idea) but it is much easier to build their church from everybody else congregations. That is why you see the inter-denominational fighting over doctrine.
Such as the Baptist tell their followers how Godly they are because they do not speak in the "devils tongue" like the Pentecostals do. The Pentecostals tell their followers how Godly they are because they do speak in tongues. (you do not have to speak in tongues to be a pentecostal they want your money either way.) But if you do speak in tongues you can't be a baptist, because you have advanced farther than the preacher and may become a threat to him so you must be removed.
But both of these denominations will attack the Catholics because of their "evil doctrine" of; "it is ok to drink." Because they are in competition with the Catholics for members. It is like their mindset is that there is only so many Christians to go around and we must compete for them. instead of going out and making brand news. (I know i am painting with a broad brush and not every one is guilty)