To be fair, this is something that was happening many many years ago. I could never understand why people spent a small fortune on a pushchair, only to swap to an umbrella fold later. And to be fair, I think to some extent the same is true today but with heavier pushchairs like the Silver Cross, Emmaljunga etc. It also happens with other brands of pushchairs, but I believe part of this is because people dont realistically buy a pushchair to suit them. One big factor is that they try a pushchair in the boot, and see that it fits - but they dont consider that you need a changing bag, your hand bag, maybe a cool bag, and there may need to be space for a weekly shop as well. Even if you have boot space, I bet all of us have stood at some point wondering where on earth to put everything in your boot!!
I also think people feel the "need" to have a pram or a carrycot for a baby. Also there are those who advocate "parent facing" for good bonding / speech development - which is important if you are out 12 hours a day, but realistically most of us spend our waking hours interacting for a good part with our child at home or elsewhere, not in the pushchair.
I also think peer pressure comes in too - from other parents but also your own parents / in laws. I know a lot of people who have a pushchair for their parents / in laws to use. I often hear people say X is wondering when they will get a "buggy".
On the other hand, if you buy the right pushchair, first time, whether its a Bugaboo or a Baby Jogger or a Maclaren, then you should have no need to swap it. The right pushchair, for your needs, and to suit your child from birth to 3/4 should never need to be replaced by something smaller or lighter. I would much rather reach for my iCandy Peach and fling it open, than an umbrella fold.
And then you have the people like me, who DID buy the right pushchair first time to last from birth to three...and would still actually be happy with that original choice, except a sibling scuppered plans and we needed a double pushchair...
Plus there are those nutters - me included who just enjoy trying different pushchairs out....
I dont think you would go far wrong with a Baby Jogger though - whether its a City Mini, GT, Elite or Versa.....whichever one suits you. They are nicer than a Maclaren :)