Probably because it's wrong. Grant was no more of a drunk than Churchill was. As anyone who has read up on either man knows. Both men drank. Both occasionally drank to excess. But alcohol did not keep either man from functioning at a high level. In Grant's case, a higher level than his Southern opponents.
He was nearly court-martialed for drunkenness, his commanders had a major problem with Grant’s drinking throughout his career and it didn’t stop during the Civil War. Grant was a drunk. You have difficulty with that because you’re afraid it’s some sort of admission of inferiority. The Union won the Civil War under the command of a drunk. I have no problem with the unvarnished truth.
“Grant was no more of a drunk than Churchill was. “
Or just about anyone else who has been through college, a blue collar/tradesman career, military experience etc.