[ssiguy]

I wouldn't say Kitchener grew from a central city. The entire Waterlo municipality is a hodge podge of different cities that just kind of grew into each other. Remember even Cambridge is the result of the merging of three different small cities....Galt, Hespler, and [I think} Prescott.
London is much more like Hamilton in that it is one large unified city that eventually engulfed much smaller satelite towns ie Hamilton's Dundas and London's Byron.
Actually it's not just a SW Ontario thing as there have only been two main growth areas in Ontario in the last 30 years, Greater Golden Horshoe and Ottawa. Ottawa being capitol almost guarantees it long term growth as government and government organizations are ever expanding and it also gets some immigrants associated with that unique title.
As for the GGH's growth it's almost exclusively Toronto centred with the exception of Barrie {which is a Toronto getaway} and KWC. Hamilton city, Peterbrough, and Niagara have grow very little over the last 30 years. Northern Ontario has shrunk in population and except for Ottawa Eastern Ontario growth in the last 30 years has been near zero.
Windsor did well in the 1990s but with the massive turn down in the auto sector it's economy collapsed and the young left. London has, since the 70s . has always been slow but very staedy growth of about 1% per year. It has also been hurt by the auto sector but London is also the areas regional, governmental, health services, and educational center. It also has a sizeable white collar economy and it is in the strategic heart of Southern Ontario for highways, rail, and passenger transport. Remember London's VIA rail station is the 4th busiest in the country.
Chatham-Kent, Lambton, Huron, Perth have has no population growth since 1980 much of which is due to all immigrants heading to Toronto and the young must leave it they want to go to university and once they are gone they ussually never come back. This in some ways also effects Windsor because for it's 400,000 the U. Windsor is quite a small school. The same is true of Elgin and Oxford but Oxford has been somewhat helped by the opening of the Toyota plant in Woodstock, and Elgin by it's proximity to London so it is getting some commuter growth which it desperately needs as unemployment is very high and still rising. London being home to both a very large and presticious university has benefited from this.
Windsor also has a similar reputation to Hamilton..........dirty, gritty. blue collar place while London has a very positive reputation. Whether these assumptions are still true is not relevant as the stigma remains.
The so called "decline" of SW Ontario is not an anamoly but rather the norm in Ontario as outside Ottawa/GTA/KWC all of Ontario has been on a very slo growth trajectory. London, considering how it has negatively been effected by the downturn of the auto sector has actually done fairly well with it's average 1% population growth per annum.