From my own experience/observations it's amazing how many punters today are not aware of betting exchanges. When Betfair first started up betting was still in a kind of golden age where bookies were busy places. Some shrewder punters saw the potential and took to the exchanges, the older majority just carried on with all the new products like virtual racing, fruit machines and older regular betting.
As time has gone on punting is in a sharp decline. I spent several hours in a bookies today to watch SIS and see my offset bets play out. For most of the time I was the only customer in the shop and this has happened in many shops I've been to (I'm sure it's not because I've not showered!).
There are fewer new punters following on from those 'old skool' crowds but they're focused more on outright gambling rather than things like exchanges which are very poorly promoted.
I think that the racing pages of the tabloids could do something to educate the newer generation about exchanges but don't seem to see that opportunity or perhaps see it as a 'niche market'.