It’s not though. It could be the point in some cases.
But often enough, constitutions have been granted as concessions from the sovereign to whatever group was putting up pressure, often the nobility, who had no further intent to introduce a republic or democracy or whatever else. Just looking out for their own interests.
The point of a constitutional monarchy is to transition away from an absolute monarchy towards a republic.
It’s not though. It could be the point in some cases. But often enough, constitutions have been granted as concessions from the sovereign to whatever group was putting up pressure, often the nobility, who had no further intent to introduce a republic or democracy or whatever else. Just looking out for their own interests.