I was actually around when this thread was initially launched and it's super funny to see it revived now. I started collecting in 2011, because steelbooks were finally a film packaging that was normed in size. I HATED thick and thin VHS covers, I despised different DVD cover-sizes and Bluray covers annoyed the hell out of me with endless amounts of plastic cover sizes and all that. It must be some kind of an OCD thing, but having a huge shelf full of movies in a collectible packaging that were all the same size no matter where they came from was hugely appealing to me. It was too bad that the movies I really liked didn't come out on steelbooks yet, it was only blockbusters and superhero titles and brainless Action flicks, but I still couldn't resist the appeal. This is why I was solely motivated by the actual and potential value of steelbooks. I missed the first wave of grails (Iron Man FS, John Rambo,...), but heavily caught the 2nd wave - especially of German releases - with titles like Room 1408, Death Race, Wanted or Hellboy 2 and also started paying premium prices for Japanese releases like the white Batman steelbooks. When I thought they had reached their maximum value point I sold them off and used the gains to buy newer, even more promising releases (Iron Man Play.com, Avengers Müller exclusive with Comic, Canadian releases like Inglourious Basterds RE, American History X...) and I was probably doing what has now and then been considered "scalping".
I decided to sell everything in 2013/14 for personal reasons (got divorced) and thought I would never be able to afford serious film collecting again. I still could not however resist buying 3 copies of Whiplash zavvi when they were on sale, because it was a perfect trifecta of a great movie, stunningly beautiful steelbook and huge potential value increase. One of the 3 came with the shrinkwrap torn and I opened it to admire its full beauty and watch the film again and as of then I was hooked and decided to somehow start collecting only movies that I really like. Now, 6 years later I have about 750 steelbooks, some open, most still sealed and have no intention of ever stopping, but still being fully aware that with all the 4K rereleases and countless Asian releases it is impossible (at least if you are on a "collecting" budget and mine is about 300€/month and I also collect Criterion Blurays and various Promo CD's...) to have a fully complete or even consistent collection.
I love steelbooks as they are the perfect film packaging. I could actually do without all the slipcovers and box sets, but I've learned to accept them (or even LOVE them with movies like Whiplash, Ex.Machina, Her and Shawshank Redemption) and now just try to buy what I like and that give me some joy when I order them, receive them and put the on the shelf.