Couplers and dividers as baluns
why do we use a different name for these kind of devices if I can already implement them with couplers and dividers?


We often name things for their function, even when we already have a name for their construction.

An "emitter follower" is just another name for a BJT used in a particular way.

A "quarter wave stub" is another name for a transmission line connected in a particular way.

And a "balun" is a transformer or other device used for a particular purpose (to convert between balanced and unbalanced signals).