It all has to do with it's value, and this matters when the property is used in a business.
When you purchase a building, your cost basis is what you paid for it.
When someone gifts you a building, they also gift you their original cost basis (what "they" paid for it.) That cost basis is further reduced by any depreciation the gift giver may have already taken.
When you inherit the building, that means the original owner passed away. In that case, your cost basis is the fair market value (FMV) of the building on the day they passed away (not the day it was titled to you.) Furthermore, any prior depreciation taken on the building by the prior owner just "disappears", goes away and evaporates into la-la land to never been seen or dealt with ever, by the beneficiary recipient of the building.
