That doesn't matter as it's only used as a boundary check and the majority of devs that fork others code are too lazy to change that.  Plus, I think it would mess things up due to POS. i.e. if that was set at 900000, then POS coins would probably not be generated and since you don't really know how many would be generated, you can't really set that to a "real" number.

The actual proof of work code determines how many coins are generated.