I can only speak of my experiences programming in Puerto Rico and República Dominicana.
In Puerto Rico, when WZNT, "Zeta", was launched in on December 29, 1978 the format included one or two merengues per hour for "variety". It only took about half a year to decide that the mix was not the best; true salseros wanted nothing to do with merengue.
When I got to Z-101 in Santo Domingo in 1976, we had a mix of salsa and merengue, about 50% of each. Some very informal research at a couple of record stores with music buyers showed that those that liked salsa did not want merengue, and the merengue listeners, the vast majority, did not want salsa. So we killed the salsa entirely... but shortly after I put together a mostly talk morning show and the station evolved into a talk format.
Oh, and I would not call salsa "Puerto RIcan / Cuban" as its origins are really New York City and San Juan, with Cuba picking up on the music as it developed.
To me, merengue is Santo Domingo, Bachata is El Cibao. Kind of oversimplification, but there is an element of truth.