Here in Vilnius naming new buildings is all the rage. They give names to business centers, apartment buildings, etc. The reason - marketing. It's easier to advertise and to sell a newly built structure if it has an attractive name with a nice aura to it.
You can hardly imagine selling a building or apartments inside of it, if there is no name on the whole structure. It's getting pretty ridiculous, actually.
And in marketing speak, it's called branding.

It is not always marketing. In England football stadiums, which have not been built in recent years, are named after the street on which its foundation was laid. Such as White Heart Lane where Tottenham Hot Spurs play. Newly consucted stadiums sell the naming the and have nothing to do wirh where the stadiums at.

Other, usually public buildings, are named in honor of a significant person in that society.

There are probably countless reasons why buildings get named after people. It may have been a trade off. Mr. Harrison will give us 2 million dollars in exchange for a room being named after him or the whole building. Many, many, many different reasons.

Maybe its because when you name something it becomes more interesting because of the history or meaning behind the name.

Some folks go overboard… In NYC alone Donald Trump has several buildings with TRUMP labelling them in giant letters. When someone mentions the Trump building you have to figure out which one.