Well to be fair cloak technology has huge draw backs so its not like they gave up this plum tech that changes the balance of power?
But it represents a formidable first strike weapon. You could sneak up on an opponent and reduce their home world to molten lava before they knew what hit them. So, if you have the technology, other powers would have to commit additional resources to vital areas to prevent such an attack.
A Klingon Bird-of-Prey sat right on the doorstep of Romulus for several days without being detected in Unification