A couple are quite expensive (thank goodness I picked them up before the current bubble), but the real issue is that Morii designed some cards that were only ever available in Japanese vending machines in the early 2000s, and the chances of ever picking these up is pretty remote
Shadowless cards were printed during the initial run of Base Set before the drop shadow was added to the card border in subsequent print runs, making them identifiable by their slightly different border design and, most importantly, the absence of the shadow that gives the variant its name
Dark Ritual The boons was one of the games first-ever cycles back in Alpha
A good portion of these are discarded due to not meeting quality standards but ones deemed passable are sent off with the normal cards
Yes, affinity can be used to lower commander tax
Jayemdae Tome is a natural inclusion, but can often be sideboarded out if you think the opponent will have loads of artifact removal, which can then become somewhat dead after sideboarding