Many people find such behaviour intrusive and provocative when they're hoping for a few minutes' peace and quiet on their way to work or wherever.
In most cases people are either nervous about confronting the noisy person or if they do they're likely to get a mouthful of abuse and told to fuck off.
Personally I'm not much bothered by noisy individuals but I can see that others might be thoroughly exasperated by such inconsiderate actions.
At least they're not having intensely personal conversations that are better aired in some more private location. I mean, do you really want the whole carriage to know that your wife is divorcing you or you've just been sacked? Suddenly a bit of restraint takes over.
Other people's quirky behaviour on buses and trains isn't a big issue for me - unless they're stripping off or puking or screaming. I'm more concerned that they go where I want them to go, they're frequent, they come at the advertised time, and there are seats available.
The days when it was customary for train carriages to be in stony silence as the passengers scrutinised their copy of the Times are long gone. Nowadays you expect a fair amount of background noise on your journey.