That'll be due to a number of factors other than just luck. Presumably you're a woman, which means you don't have any nuts that can get squashed and so you probably, like most women tend to do, sit with your legs crossed or closed, which takes up little space and so you don't come into contact with your neighbours even though they're probably interloping in the space in front of your seat. Also, chances are the men are more respectful around you because of your gender, and so there's none of the purposeful pushing that goes on.
Another thing is that you're at the civilized end of the route, suits and shoppers. I'm at the 80% black, Turkish and Eastern European end. Many of those people are completely lacking in manners. Especially the men in their twenties.
Only had one problem that I can recall with an Anglo-Saxon. The rest of the time it has been one of the three groups mentioned above. Those Eastern Europeans are bad. I get it from them on the District Line too, mostly construction workers early in the morning.
Stuck up?! I couldn't give a fig who sits next to me; I just don't want them taking up my space. Your size be damned; any man of above average height wants to be able to space his legs out, and on the bus no bugger should take up another man's space as defined by the seating arrangement! Even if you're 6'6" you can still make yourself fit within the allotted space, so bally well do so!
You suffer for your size, as there's no reason why I should have to in your stead!
If you don't like it, complain to the bus company instead of trying to force my leg further into my own space so you can appropriate some unjustifiably!