Strange it doesn't do local, but I imagine there are legacy reasons for that. Everything in Office is old. Often it is crazy well engineered, but decisions set in stone decades ago still linger on.
Well engineered and coded decisions made in the age of single user desktops are still well engineered. Hard for someone in 1995 to predict the need for a file format that supports real time coauthoring with automatic saving and complete revision control of every edit.
Esp. when the target machine the code had to run on was a 486 with a slow hard drive and a tiny bit of memory.
Of course Office updated their file format, but they probably did it a little bit too soon. I always wondered what would've happened if they had waited a few more years, released in 2007, so probably design started a few years prior. Talk about just being a smidgen too early for a world of unlimited(-ish) data and always on internet connections.
Strange it doesn't do local, but I imagine there are legacy reasons for that. Everything in Office is old. Often it is crazy well engineered, but decisions set in stone decades ago still linger on.