In the Cubase 9 demo vids it shows the user cut some audio (in this case a note from a bass guitar) drag it into the sampler and then played that note at various pitches.
When I cut a small section of audio and drag it to the sampler it loads up the full track? Is there something I am not doing.
bounce your cut selection before you drag it to the sampler track.
Hopefully direct dragging from a range selection will be available in upcoming releases!
I’d love to see a velocity curve adjustment in the sampler as well !
That being said … I’m loving this new Sampler feature!!!
I’ve just spent an hour playing with a single D.I. electric guitar note and VST Amp Rack and some delay, reverb and soundtoys sends coming up with some awesome new ideas and sounds!
Quick Tip:
add an audio track with “No Bus” out and “Outputs - Stereo Out” input and hit record for realtime recording of the sampler audio out,
or create exclusive FX sends for your sampler track and create a new Group Track with No Bus output. Then edit the channel settings in sampler (where’s the direct routing steinberg!???) to pick a new Group track target. Direct your output of your exclusive sends and the sampler track to the group track. Set the input of an audio track to the Group Track used and the output to your Stereo Out.
Play / Record along live with your other tracks to come up with ideas!!
Now we need a “ReSampling” track type that can take input from any other track or out! 
bounce your cut selection before you drag it to the sampler track?
I don’t understand what you mean by this?
Also if the feature of drawing a small section of an audio file into the sampler and playing it is not available - why does it show it on the video advertising Cubase 9?
When you’ve made cuts to or resized an audio event, it is non-destructive in Cubase. Which in simple terms means it is not affecting the original audio file.
If you drag a cut section to the Sampler it still sees the whole original audio event. To make it see a smaller audio event matching your cuts (and fades, etc) you need to select the trimmed event and right-click the event and select Audio → Bounce Selection (or do so from the menu system on the program top bar). This creates a new version of the original that is sized to your cuts and replaces the event on your playlist/arranger view.
When you drag that to the sampler the audio in the sampler will match the event you dragged from.
I don’t work for Steinberg so I can’t comment on reasons for marketing videos!
But I agree with you and would like to see it also work from the range selection tool,
Where I can select a section of an event and drag it directly to the Sampler track and have just the selected audio in the Sampler.
Thank you for the help.