One of the reasons is because your society is based more or less on cooperation while ours is based on competition. "How so" you can ask, "you are a post communist country, where did this competing spirit come from and why in elderly people?"
The answer is that in communist times all the good things were restricted. If you want to have a car, you had to wait for years even if you have the money. If you want to eat bananas you had to wait for november and december and if you had to wait on big queues. If you want a colour TV you must have a good relations with some "people" to have it.
At that time the system of "connections" emerged. Everyone formed a "circle" of other people that he can trust. All the really good things were sold "under the table" and only to a people that are in your circle. After that you repay the service by giving then something that is connected with your profession.
So after living 20, 30 years in such society you start to percieve the strangers around you as competition for everything. Add to this also the traditional Bulgarian thinking:
"We are all equal (this is the main communist dogma) and how come someone else have more than me - he is certainly a criminal or have better connections but he does not deserve to have more than me" and you will start to understand some of the reasons behind pushing the rest while getting on the bus.
Some other indications for the competitiveness of our society can be seen in the sport - most of the big sport achievments in Bulgaria are individual, not team based. We have the world record on women high jump; we had some of the best wresters, some of the best heavy weight lifters and they are all really good, having several world and olympic titles. Compare that with team sports - we have been fourth in the world in soccer and several times second/third in volleyball.