I call it laziness on the part of the presenter.
My wife has been program chair for a national healthcare professional's conference for years and from what I gather it is the rare presenter indeed that does not have at least their power point slides available.
I have noticed at national and regional conferences the more experienced the presenter the more likely they are to have handouts.
I know you are torqued there Fatcord, but no need to jump completely all over Cerviarb. On the surface his "lame" comment may not seem pertinent to the thread but he does bring a couple of good points. Certainly some note taking supplies could/should be available but then again, why would an attendee not come prepared?
Since you have spent good money for these seminars and yet feel you are not getting your money's worth there are several options available for you to change that problem.
First is fill out the comments forms and bombard the organizers with notes, comments and emails telling them what you expect!
Second is to go up to the presenters and ask if the ahve anything . You can also ask them during the Q&A session in front of everyone else. It may spark them to make something available.
Third, you might want to start being more particular about what seminars you go for. If you are not getting your money's worth then you really ought to consider not spending your money on them.
Part of the reason some conferences are so durned expensive is the rules under which some of the conference centers have to work.
For example at some of the conferences my wife sets up if a projector blows a bulb they cannot simply walk into one of their other rooms and grab that projector.
There are specific facility employees that have to do it and they are billed for it. Sometimes we're talking in the hundreds of $$$ just to get some equipment moved around.
Anyhow, there is a lot going on behind the scenes and at the regional or local level it is difficult at best to get quality speakers.
I'm not making excuses, you still need to let them know your thoughts, but there are things going on that makes what you are asking for not necessarily a simple fix.