By that I mean, when we ask the majority of the population they probably aren't going to be willing to pay for something just to use their own money, they would rather have third parties which handle that for them.
Not wanting true decentralization doesn't mean hell-bent to lose self-custody. I believe the majority of the users, excluding those who're here just to trade, use SPV clients as it's the easiest solution with the least risks.
Those who leave them on centralized exchanges haven't understood what they've bought.
Thoughts?
I think the storage cost has little matter. Running non-pruned full nodes definitely helps the network, but if the user doesn't want to buy an extra hard drive, they can get the same features by running a pruned node with txindex=1.