This is probably because of the amount of 3rd party MS office Applications in the market developed by different individuals and making loads of money from its sales.. Trust Microsoft to be the party Crasher.
I Did a search for "Microsoft Office" on the Google Android Play store - and was bombarded with trial versions and expensive applications that claim to be alternatives to excel, Word, Powerpoint. After several (Free) downloads - Found the perfect FREE Microsoft Office Application for Android - Its called "KingSoft"
PC world wrote extensively about the Best Paid Office Alternatives for androids (It looked like a sponsored review tho) - But now I'm telling you about One FREE Good Office alternative for android.
It Supports 23 kinds of files, Inputs formats DOC/DOCX/TXT /XLS/XLSX/PPT/PPTX/PDF and outputs formats Microsoft Word, Excel and PowerPoint 97 to 2010 formats: .doc, .docx, .txt, .xls, .xlsx, .pptx and .pdf.
Download Kingsoft from the Android market on your phone Or Directly Download the APK version of Microsoft Office Alternative by Kingsoft