catpower1980: As pointed in the video, the new form of demos actually are the mobile games with in-app purchases and in that particular market that makes sense because:
1.technically, due to the various you'll never be 100% sure that your game will work correctly on most devices.
2.consumer's habits: people almost spent no money are more likely to throw 1$ here and there than paying 5$ upfront.

Now, on the PC market specifically:
1.sharewares was useful to get known in the 90's because of the lack of internet, now there's youtube, twitch.
2.consumer's habits: games are to gamers what clothings are to women: driven by sales and impulsive buys.

The state of PC demos nowadays from a dev point of view:
1. Demos are now mostly used for tech/gameplay demos to promote crowdfunding campaigns. Sadly, early access are now the "new demos".
2. Most games rely on upgrades and unlockables so if the demo features only the beginning of the game, it will lack most of the features and run the risk of feeling too generic (like every metroidvania starts with only "jump and shoot" option)
3. The best way would be to design a specific level which would showcase every features of the game but it can heavily backfire as the level design and game balance could be completely different than the real game experience.
4. the best genre for demos are point 'n' click which only features the beginning of the game as the player can directly experience the flow of the story and get involved in it or not.
5. Money Shark mode on: a PC consumer will more likely buy a 5$ game on sale than properly taking the the time to install a demo and play it so it's better to not refrain him from his purchase. Of course, for a 30-60$ price, it's another matter but as most games cost less than 20$....

Conclusion : IMHO the only future of PC demos are through web games (no install, direct gameplay) without forgetting to put a visible buying option. See how Winter Wolves did it for Vera Blanc:
http://www.winterwolves.com/webgames/verablancfullmoon/