For as long as we know, we’ve been saying a brachah on it. To the best of my knowledge, that’s a mesorah.
It is not like the story of the rebbe who would cut his nails after going to the mikvah. One chassid begged the rebbe to tell him the sod.
The rebbe told the chassid that he will only reveal it to him after fasting for forty days.
After fasting for forty days, the chassid asked the rebbe for the sod. Answered the rebbe, “because then my nails are soft”.
But we should assume that we wouldn’t have anything but a true mesorah on marror with a brachah.