Why does the Hollywood film industry focus so much energy on remakes and reboots?

Because they are low on new ideas. People trying to recreate Nostalgia.

There have always been reboot/remakes for as long as the film industry has existed. This is nothing new. The vaunted Wizard of Oz, starring Judy Garland, in addition to being an adaptation of a book, was no less than the 7th film adaptation of that book. A remake of a remake of a remake of a remake…..

Nostalgia sells tickets, whereas an original story is an unknown quantity.

Not every new story will be the next big thing, and flops are expensive.

brand name recognition

Money.

The latest incarnation of Mad Max to me had very little soul of the original Mad Max, it was more of a remake using the same character and theme but not a remake of the same movie. It was like seeing the movie spoiler alert Jaws, then having the chance to actually read the book and it was like Bizarro world, the movie seemed to flip things in the book around 180 deg. Then some movies are like stand along movies along the same theme, you can watch the latest and follow it without seeing the ones before. As to the OQ, I believe Hollywood remakes and regurgitate old movies because they believe they have a proven track record. Everything old is new again. They can redo and present a movie to a new audience of another generation that may have no or little history with the original other than hearing mom and grandpa speak of it. Unless a movie is so innovative and different I believe Hollywood would miss how great it might be chasing the buck with the tried and true. Certainly there is more content in books and original screenplays out there I believe they are missing.

Remakes are generally cheaper to make than originals.

Poverty of ideas and appetite for guarantees. Before selling to the public, moviemakers first have to sell to backers, and tried-and-true appeals to those who are taking the financial risk.

They sell

OMG I like the question in general but I loathe the Star Trek reboot and was very disappointed with Mad Max.

But ya, what @Jeruba wrote. They are industrialists and investment managers, not artists.

In all of the years of movies and television, all possible scenarios of all possible genres have been covered. The bottom of the barrel has been thoroughly scraped. What else could they possibly do???

I have pondered this also. Here is what I settled on in my head. (you know- important things!) I was speaking to a close relative. It was the Xmas season, and everyone has their favorites in holiday viewing. I usually hit up TCM for uninterrupted showings, if I can find the remote. We were mentioning some older films. I said that I always liked The Bishop’s Wife. Black and white, Loretta Young, Cary Grant, David Niven, et al. So, that year, when on TCM- they watched it- and hated it. I told them the were communistic bourgeois pig-swines out to ruin the holidays. Actually, they did not like how hokey it looked as CG was decorating the Xmas tree via ‘angellic licensure’, or when the cab driver was ice skating- surely everyone knows that it’s not the actor-too professional! I said – yes- all magic for 1947! Then I turned to their beloved Star Wars movies. ( this is considered as Spiritually Devine and none shall question His Holiness- George Lucas!!!) So, I sharpened the stick and poked. “So, uh, the effects of the first released SW is as blessed as the very last of the screwed up order of the third of the first set, released???” (!!!) Thrust and parry! The debate was on…ha-ha!
Everyone looks at a successful film from its own release date, and thinks they are starting out with successful ” for that time back in the beginning stages of filmaking and dinosaurs walking the earth ” and gosh, with new effects, lighting, more money and better (?) actors- that then- when the Newer Version is released it will be on par with the other two films out of 10 bazillion which successfully surpassed the original in All Areas!!! It doesn’t, and it won’t. But hope springs eternal from the movie-industry’s cold metal heart.
@NerdyKeith- An Aside- the brother of the aforementioned family member is a phenom in the making of movie trailers. No, not what they live out of of, but rather what heathens like myself call – movie previews. He’s really good. ( but I changed his diapers- so, whatever…) When creating new trailors for remakes of older films- some (him) go back and watch the trailers from the first release of the original. Producers and Directors usually do Not want them to be even closely related to the original. While others- why change success? just update it. One really must know the industry and it’s people when navigating the business. Yikes! ( sorry for the length of the epic- coming to theaters in film format soon!)

Built-in audiences. A producer’s favorite three words.

Someone above said sequels are often cheaper to make. Sometimes true, but usually, if a movie did well, especially if it’s a blockbuster, its sequels get bigger budgets to pay for many things including the same actors’ increased salary demands ramped up special effects, often more shooting locations, etc. The various Superman franchises are a good example of that.