What is with all this military branch rivalry?

i actually have 2 questions for you folks here today, so let me get started with my original one, and that is why is the only armed forces commercials you see for marines, and i mean literally thats the only ones you see, its been at least a year since ive seen an army commercial, and the next one came about when i was looking into the first one, all i found on the internet was people bad-mouthing the army and saying that people in the army ar fat asses and some bullshit like that, and whats with this stupid acronym that army stands for aint ready for marines yet?, i bet if a soldier in the army heard that they'd kick whoever said it in the face. And the general assumption that because the army takes for casualties means there worse soldiers, i mean comon, for one thing theres more of them and secondly there in an area for long periods of time, now please dont get mad at me or call me ignorant, im just curious as to why the real ignorant people who compare branches of the military do this.