This highly relevant answer
gives us two good reasons which I will embellish a bit to more directly address the question at hand:
1. Outside of the (quite austere, I might add) Romulan Empire, Romulan Ale is scarce
Scarce alcoholic beverages are valuable since as soon as there are more people who would like to try it than there are units available, they start to outbid each other. The Romulan Empire could capitalise on that if allowed to trade Romulan Ale if the replicated ale lacked something. Which brings us to the second point...
2. The replicated ale (if available in the databank at all - the standard is that it is not) does lack something.
It seems what makes Romulan Ale so highly sought after is that it got a unique strength (euphemistically called "aroma") which kind of hits you like a truck. The linked answer quotes a Romulan
officer senator (cheers @ Valorum) commenting on the replicated version in DS9, saying that it was
...somewhat lacking in aroma. Real kali-fal should forcibly open one's sinuses well before the first sip (emphasis mine)
This basically means that whatever the replicator produced here, it lacks that what makes Romulan Ale unique: that it can knock people like Worf out in no time - the special kick it will force upon you before you even took the first sip.
Therefore, it makes sense to have a trade embargo which involves Romulan Ale. Well, and you would probably have quite a few addicts lying under the counters (or their own tables) all over the federation in no time. Imagine what this might do to a mere human only used to synthol if it knocks Worf out like that. Medical attention would probably be mandatory.