YABVU and ridiculous.
If I couldn't have taken an unfolded pushchair on the bus I wouldn't have been able to go anywhere when each of my kids were born: heavy babies and c-sections both times.
When ds was about 2 and I was (heavily) pregnant with dd I used to have to take a non-accessible bus to a toddler group once a week and it was a nightmare (but I was so exhausted from the pregnancy that it was actually better than the accessible bus and walking option!). It was really difficult, even with an umbrella style buggy, as ds was a bolter. Sometimes people helped me, and I really appreciated it, but mostly I just had to manage on my own and it was a stupid waste of time and effort compared to being able to just push and park a buggy on an accessible bus.
I too loathed the monster prams, with both kids we had as compact as we could that did the job they were needed for. Unfortunately, I needed a pushchair with dd much longer than I would have liked because I didn't have a car but needed to get to places within specific time slots. As mentioned earlier I have heavy kids, and it got to the stage where I physically couldn't push her in the compact, manoeuvreable, bus-friendly buggy and I ended up having to get a second hand monster pushchair. It was an absolute pain on the buses but, without it and the accessible buses, work and school pick-ups would have meant I couldn't take her to her regular toddler groups, or meet up with friends, or go out for the day. Carrying her wasn't an option, she was much too heavy, so if we went out she would still need the pushchair for when she got tired. I had to use it until the summer just before she turned four and was really glad to finish with it.
I only once had to get off the bus to let a wheelchair user get on, but I accepted that that was just one of the inconveniences of having to use that pushchair and was grateful that it only happened once. I do agree though that anyone travelling regularly on the bus should get something more bus friendly but I think until you actually travel regularly on the buses you don't appreciate what works best and if you've already spent a fortune on a flash pram it's hard to justify buying anything else.