Firstly, I am not 80! So your math is a bit off.
I am not gonna sell you on it (partly because people make their own choices, partly cause it is not my job to do it and, mostly, cause your preconcieved notion of Brampton is hard to shift in all likelihood...and that is fine). As for me/we....why does anyone live anywhere? We enjoy our day to day lives....it has the right balance of "stuff" for our family......the school system works for our family....there is stuff to do....it is reasonably proximal to other areas we want to go to......we enjoy the cultural/ethnic diversity of the place......we like our house, we like our neighbours(hood) and it is home.
There is stuff we don't like too (we don't like having the highest residntial tax rates in the GTA...but we understand why it is so.....we don't like being the worst served community - relative to population - by provinicial responsiblilites like GO Transit, lanes of highway and hospital beds) but most of those are (IMO) just a function of Brampton's growth coming so fast and at a time when the funding of things follows a different model (unlike, say, Mississauga which grew earlier and in a time when the provincial government had more of a "you got people...here, have some hospital beds" kinda fiscal attitude).
As much as we like the place we also think the potential is greater than is being achieved now and we enjoy seeing the struggle to "get there".
Honestly, the city takes a lot of "shots" like the one you delivered and I often wonder how many people making those shots have ever been to Brampton. (that is not a shot back at you but just an observation over the last 40 years).
So, yes, people do choose to live there.