I agree with you - the power to have stronger upvotes, especially when combined with the ability to self-vote (although "good" users won't overdo it), creates a huge incentive to hold Steem for the long term. These holdings never need to be cashed out to get value from them, which is insane.
I'm definitely trying to get as much SP as possible now while it's still the early days - it's gonna be much harder in a few years.