There are so many reasons I believe.
Dust collection is maybe the first thing people think of, but its more than that, it a complete system. they just don't build a good saw or router, or any of the other fantastic tools, they think about how they are used and they work great together, it does not matter if you are in the shop or in the field. I make my living from using these tools, and yes I could do a lot of what I do using other brands, but I could not do it as safe, as quick and as clean as I do with the Festool system, about the only two power tools I take to the jobsite that are not Festool are a portable table saw for ripping narrow stock and a miter saw for cutting moulding, but it looks like one of those will be dealt with soon. I just have to decide wheteher or not to have a family member bring the CS50 or the CMS system, but boy are they expensive in the UK.
I think the Plug-it system is another great idea, it is sooooo much easier to just pick up a tool and switch plugs at the tool end rather than finding the plug end, you have one cable instead of a rats nest which is so easy to trip over. And thats just the tip of the iceberg.
The only other thing that would be nice to see is the belt sanders, although I don't use one very often, but it would be good to see them here.
Regards
Paul