Immigration is also one of several drivers pushing up house/land prices. Gently applying the hand-brake to immigration will help take a little heat out of the housing market without popping the bubble.
The problem for the government is striking a balance between reducing pressure on infrastructure/housing and increasing pressure on employers.
These tweaks are necessary from time to time to keep things in balance.
These tweaks are necessary for the government because really poor infrastructure planning & cheap way to get votes with no vision. That is all.