Why is the entropy of the universe so much lower than the Bekenstein-Hawking boundary entropy of the cosmic event horizon?

Currently, the most upvoted answer to the question What is the entropy of the universe today? cites a 2010 paper by Egan and Lineweaver, which estimated the entropy of the observable universe at about $10^{104}$ bits. However, the Bekenstein-Hawking boundary entropy of the cosmic event horizon is much larger, about $10^{123}$ bits. Why is there such a large difference?

I understand that the event horizon of a black hole is not necessarily analogous to the event horizon of the universe, so if I am making an inappropriate comparison, I’d appreciate being corrected.