By most accounts, Apple still has more than half of the tablet market locked up. Most of the rest is taken by Android or Android derivatives, and Office isn't available on that platform, either. Yet people keep buying tablets like they're very much in style.
Microsoft still sells copies of Office hand over fist; but until the release of the Surface, the productivity suite was almost completely absent from a market that continues to increase in popularity every day. (The exception consisted of legacy Windows-based tablets, which don't even register on the sales charts.) It's not like the Surface has been a barn-burner, either. (Microsoft has not released figures on how many barns the Surface has burned down.)
In the last 15 years, Microsoft Office has gone from a must-have product to largely irrelevant to the success of the biggest product category in technology: mobile computing. Derek Kessler believes that, by shipping Office for iOS, Microsoft could have furthered the impression that the suite is essential, but I think the shift is more fundamental.
A word-processing application was necessary back when printing was a daily activity. Heck, we'd print all kinds of ridiculous things in the '90s: résumés, term papers, holiday letters, dungeon master's character sheets ... uh, I mean, résumés. Résumés.
But eventually I, like many others, simply stopped needing to print. Everything I wrote I transmitted electronically or put on a webpage. And really, good riddance to printing. Printing is horrible. Printers are horrible. Printing software is what people in Dante's Ninth circle of Hell are condemned to use over and over. A pox on you if you ask me to print something these days; a plague on you and your house if you ask me to fax something. A good text editor--BBEdit, or any of the dozens of excellent Dropbox and iCloud-based iOS editors--is now my writing tool of choice. Memorize a few pieces of Markdown syntax and kiss a "word processor" goodbye.
Having exorcised the word processor, we're left with the Tito and Jermaine of traditional office suites: the spreadsheet and the presentation application. Personally, I only use a spreadsheet when I'm running low on money. I still need one, because I frequently run low on money, but for $20 Numbers offers more than I need. As for presentation software, do I look like I enjoy public speaking? With a chin like this?