There's no valid reason why the attacks in these demonstrations and videos could not be more realistic. In terms of the excessively co-operative uke, perhaps some middle ground needs to be reached between resisting the technique and excessive co-operation, for the purposes of the demonstration or video. I know the demonstration or video would be less spectacular, but it would be more realistic. When a potential student is contemplating doing a martial art, one of the first things they often do these days is get on the internet and research it, which includes watching these you tube videos.
Not having been a potential
student of martial arts for a while now, I can't really state definitively what most of them are doing these days
However, I do know that there's a danger in making assumptions about how other people's minds work. For example, you say that demonstration attacks could be "more realistic". But to an uneducated person who isn't a brawler, what does that mean? A person without experience or knowledge will not have an informed judgment about what's "realistic". They might be able to differentiate between "resisting the technique" and "excessive co-operation" at the extremes, perhaps...but again, there's that pesky "realistic" thing (how "realistic" is an extreme, almost caricatured situation?). So do you show them what they think
is "realistic"...or what you
think they think is "realistic"...or what?
It's not a new problem and it's not unique to aikido.