Roll away the dew.
It seems like the reasoning runs that they gate character development behind restricted books, and then use a flurry of events to drive the player base to engage constantly in the early days of the game, presumably to inflate the number of store transactions as people pay to speed up progress.Honestly (and I can't believe I'm typing this), I'm starting to feel a little burnout from the events. Or maybe it's just a lot of concern about it. It's early, but we seem to be having an event just about every other week. Don't get me wrong - I'm loving the scrolls and restricted books, but with Portmanteaus being such a big part of it, silver keys are being more and more valuable, and I can see it easily getting to the point where any coins earned go towards buying enough keys to finish that part of the event.
Personally, I've had my fill of the screen being flooded with purple foundables every other week. They're starting to feel like a distraction, requiring a good deal of effort that doesn't go toward the larger goal of filling in the main registry pages, which, as you say, are going to take months to fill out before getting to prestiging.