I like that I can select a room that faces the direction I want (i.e. not towards the major road etc) if necessary. All goes out the window if I reach the front desk and am reaccommodated anyway (either upgrade or "your selected room is not yet available, but I can offer you this other room of the same category")

Digital key is great in theory but doesn't work for me in practice even if (and that's a significant if) it "works" at all.

The numbers I don't find suprising at all. The more one stays in Hiltons, the more likely it is one has HH card. And more of an impact on total occupancy ratio.
Frankly with the ease of registration I am surprised it's not more than 64%. But then I also know people, even quite regular business travellers, who don't bother with loyalty programs... which I find weird especially for hotels. One two-week trip to London or Stockholm and you bag enough points for a free night, barely knowing how it happened.