I am reliably informed that because so many strata schemes left this to the last minute, installers are over-subscribed and that allows them to ramp up their charges, if they so desire.
Who’s to blame? The backsliders and foot-draggers would have to accept their share.
Also, strata schemes can just employ tradespeople to install locks and can even pass the responsibility on to individual owners via a by- law. Have a look at this factsheet