Explain it to me like I'm stupid

I've seen an understandable uptick in ruby/steel or steel/whatever challange decks and Thebes seems to be missing from most of them. When I switched my Ruby/Amber deck to Ruby/Steel this was one of the first cards I thought of. Why isn't this card used more?

I've seen an understandable uptick in ruby/steel or steel/whatever challange decks and Thebes seems to be missing from most of them. When I switched my Ruby/Amber deck to Ruby/Steel this was one of the first cards I thought of. Why isn't this card used more?