At the highest level of play, I don't think anyone is going to decline purchasing anything. Even if you don't build a monopoly, properties are invaluable trading tools -- there's no reason not to buy everything you can. You have to be a little smart about it, but I'd say the general rule is that you want at least one property from all the non-ghetto areas.
Like most card games though, I suppose Monopoly is more fun when not everyone is playing at the highest level.