In Standard, even Khans Standard with fetch lands, it took some effort to make Treasure Cruise and Dig Through Time cheap
This would lead to Mox Opal eventually being banned in the format, cementing it as a clear powerhouse for all time
That meant we really only had "boy king" and mummy to work with, so we ended up making him a commander for embalm, putting him into the two colors that focused on the mechanic
It's mostly found in artifact decks or those with prison elements like Chalice of the Void and Trinisphere
While today, we expect reprints on a yearly or even monthly basis, and much of the player base clamors for more reprints of in-demand staples, at the time, the idea of a high-supply reprint set was completely new
The other way you want to look at your ultimate is in contrast to the other things your planeswalker does